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NOTES 


ON 


DENTAL  PORCELAIN 


A  PRACTICAL  TREATISE  ESPECIALLY 

DEVOTED  TO  THE  INTERESTS 

OF  THE  BEGINNER. 


BY 


V.  WALTER  GILBERT,  D.D.S. 


OYER   ONE  HUNDRED   PRAGTIGAL  ILLUSTRATIOXS. 


SECOND  EDITION. 


PHILADELPHIA: 

THE   S.    S.    \VH1TE   DENTAL  MANUFACTURING    CO. 

LONDON : 

CLAUDIUS    ASH    &    SONS,    LHUTED. 

190C. 


^ 


COPXEIGHT,     1905,     BY     V.     WALTER     GILBERT. 

copyeight,   1906,  by  v.   walter  gilbert. 
Entered    at    Stationers'    Hall,    London. 


M 
O 

o 


IN     LOVING    MEMORY 

OF 

MY    DEAR   FRIEND   AXD   BELOVED    I'ltEL'EPTOK 

Sr.   iEU   (B.   i'larr 

THIS    BOOK 

IS   AFEECTION'ATELY   DEDICATED 

BY 

THE  AUTHOR 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 

Open  Knowledge  Commons 


http://www.archive.org/details/notesondentalporOOgilb 


INTRODUCTION 


Notwithstanding  tlie  fact  that  literature  upon  the 
subject  of  porcelain  work  has  been  much  in  evidence, 
there  has  api^eared  little  information  which  is  of 
value  to  the  beginner  in  this  class  of  work. 

A  student  or  practitioner  desiring  to  make  a  start 
in  the  practice  of  porcelain  work  is  wafted  about  by 
the  opinions  of  others  like  a  voter  who  listens  to  polit- 
ical ''spellbinders."  The  opinion  of  the  high-fusing 
enthusiast  is  accepted  only  to  be  discarded  upon 
reading  or  hearing  the  opinion  of  the  low-fusing 
enthusiast  and  vice  versa.  The  wonderful  assurance 
with  which  the  different  manufacturers  make  use  of 
the  word  "best"  is  calculated  to  mystify  the  inex- 
l)erienced.  In  the  following  pages  the  author  has 
endeavored  to  describe  the  uses  of  the  different 
grades  of  porcelain  and  to  explain  the  principles 
underlying  their  application. 

The  many  porcelain  compounds  now  found  on  the 
market  cover  a  wide  range  of  adaptability.  The 
characteristic  working  qualities,  the  difference  in 
glazing  point,  the  capability  to  withstand  practical 


manipulation,  and  the  character  of  each  compound 
when  viewed  in  the  finished  work  make  it  important 
that  a  study  of  these  essentials  should  precede  prac- 
tical application. 

An  effort  has  been  made  in  this  volume  to  present 
the  subject  in  a  manner  which  will  be  fully  under- 
stood by  the  novice  as  well  as  by  the  practitioner  who 
is  more  or  less  familiar  with  this  branch  of  dental 
practice.  A  study  of  porcelain  as  outlined  in  the 
chapter  on  "Laboratory  Experiments"  will  aid  in 
clearing  up  many  things  which  are  not  fully  under- 
stood by  the  general  practitioner. 

Many  of  the  little  things  heretofore  omitted  be- 
cause of  their  seeming  unimportance  have  been  in- 
cluded because  as  a  matter  of  fact  these  little  things 
are  of  vital  importance,  especially  to  the  beginner. 

Many  of  the  illustrations  are  original  and  were 
made  for  this  book.  These  original  illustrations  to- 
gether with  those  made  possible  through  the  courtesy 
of  The  S.  S.  White  Dental  Mfg.  Co.,  The  Turner 
Brass  Co.,  The  Eansom  &  Randolph  Co.,  Klewe  &  Co., 
and  Mr.  H.  J.  Caulkins  will  aid  to  a  great  extent  in 
an  understanding  of  the  text. 


CONTENTS 


PAGE 

Introduction    5 

CHAPTER  I. 

Porcelain — Its  Place  in  Dentistry 9 

Porcelain  Dentures    10 

Porcelain  Crowns   12 

Porcelain  Fillings 14 

CHAPTER  II. 

Dental  Porcelains    15 

Block  Bodies — High-Fusing  Porcelain — Low-Fusing  Porcelain,  16 

High-Fusing  Porcelains 18 

Low-Fusing  Porcelains   20 

CHAPTER  III. 

Laboratory  Experiments   22 

Test  for  Shrinkage 24 

Test  for  Glazing  Point 24 

Tests  for  Relative  Firing  Point 25 

Test  for  Contouring  Qualities  and  Color  Stability 33 

CHAPTER  IV. 

Practical  Application  of  Block  Bodies 36 

Former  Conditions 3G 

Qualities  Required  in   Block  Body 37 

Making  Porcelain  Compounds 38 

Practical  Application  of  Block  Bodies 39 

The  Use  of  Silex 41 

Firing  the  Body 42 

Enameling    42 

Staining  the  Teeth 43 

Firing  the   Enamel 43 

Cooling   Porcelain    44 

Artistic  Study 44 

Possibilities  Afforded  by  the  Manufacturers 45 

CHAPTER  V. 

Porcelain  Crowns   46 

The  Turner  System  for  Making  Crowns 47 

Practical  Application    48 

Solid   Shade  Crowns 50 

Shading  the  Crown 51 

The   Use  of  Facings 52 

Metal   Framework    53 

Applying  the  Porcelain 54 

Firing   the   Crowns 55 

Crowns  for  Exposed  Roots 57 

Porcelain  Crowns  with  Gold  Bands 59 

The  Use  of  Pinless  Crowns 61 

Attaching  Pin  to  Crown 63 


CHAPTER  VI.  PAGE 

PoltCELAIIS'    FiLLIAGS     64 

Value  of   Porcelain 65 

Experimental  Work  67 

Technic  Teeth   68 

Cavity  Preparation    68 

Tj'pical  Cavities   70 

IMaking  the  Matrix 74, 

Annealing  Platinum  Foil 15 

J^ental  Lac  as  a  Swager 77 

Gum  Camphor 78 

Taking  Impressions   78 

Ash's  Swager 80 

Application  of  the  Porcelain 81 

Tlie  Initial  Firing 82 

'i'wo  Methods  of  Building  Inlays 82 

Shading  the  Inlay ■ 84 

Cementing  the  Inlay 86 

CHAPTER  VII. 

Shading  Poucelain  80 

Unnatural-Looking  Crowns    89 

Making   Shade    Samples 90 

Something  ]\Iore  than  Shades  Required 94 

CHAPTER  VIII. 

MiMiKAL  Stains 96 

Individuality  of  Teeth 96 

To  Effect  Changes 97 

Tlie  Stains   101 

Practical  Application    102 

Firing  the  Stains .- 104 

CHAPTER  IX. 

Furnaces     108 

Operating  the   Revelation   Furnace 109 

Electric   Furnaces    109 

Gasoline  Furnaces    114 

Gas  Furnaces    :  ....  116 

CHAPTER  X. 

Firing  Porcelain 119 

Methods  for  Determining  Glaze 121 

Time  and  Eye ^ 122 

Porcelain   Cones    122 

Gold  and  Time 123 

Pyrometer  JNIetal    124 

Pyrometers     125 

CHAPTER  XI. 

Suggestion   for  Using  Thermo-Electkic  Pyrometer    126 

Testing   the    Muffle 130 

Testinaf  the  Porcelain 131 


CHAPTER    I 


PORCELAIN— ITS  PLACE  IN  DENTISTRY 

A  quick  and  an  effective  way  of  ascertaining  the 
relation  and  value  of  any  article  to  a  given  subject 
is  to  imagine  the  conditions  which  would  exist  if  that 
article  was  no  longer  obtainable. 

Imagine  the  condition  of  dentistry,  were  all  the 
artificial  teeth,  porcelain  bodies,  gum  enamels,  etc., 
destroyed  and  no  longer  obtainable.  Think  it  over 
and  you  will  be  pretty  thoroughly  convinced  that 
no  value  can  be  placed  upon  the  opinion  of  those 
who  say  '* Porcelain  has  no  place  in  dentistry." 

Ever  since  artistic  dental  prosthesis  became  a 
possibility,  porcelain  has  held  an  important  place  in 
the  profession;  in  fact,  dental  jDrosthesis  is  today 
impossible  if  we  do  not  make  use  of  porcelain.  No 
one  will  deny  the  fact  that  porcelain  is  the  best  mate- 
rial with  which  to  construct  artificial  teeth.  By 
reason  of  their  physical  resemblance  to  the  natu- 
ral teeth,  and  their  other  essential  qualifications  of 
strength,  resistance  to  oral  secretions,  etc.,  porcelain 
teeth  are  used  in  constructing  the  artificial  dentures 
of  civilized  humanity.  If  the  ' '  ready-made ' '  artificial 
porcelain  tooth  was  the  only  thing  made  possible  by 
this  material,  the  profession  would  have  much  for 
wliich  to  be  grateful,  but  with  porcelain  other  dental 
desiderata  are  made  possible. 


10  GILBERT "s    NOTES    ON    DENTAL    PORCELAIN 

Porcelain  The  modern  continuous-gum  denture, 
Dentures  when  properly  constructed  with  a  porce- 
lain compound  specially  made  for  the  purpose,  can- 
not be  equalled  in  point  of  cleanliness  and  natural 
appearance.  Porcelain  of  itself  is  clean,  it  presents 
a  surface  which  is  smooth  and  if  glazed  is  impervious 
to  moisture,  it  is  to  a  large  extent  translucent,  and 
capable  of  being  pigmented  to  reproduce  the  appear- 
ance of  living  tissue.  A  denture  made  entirely  of 
porcelain  like  the  Dunn  Mineral  Plate,  or  a  denture 
made  by  firing  porcelain  upon  a  platinum  base  like  the 
modern  continuous-gum  plate,  comes  nearer  to  restor- 
ing natural  conditions  than  can  a  denture  made  of 
any  other  material.  As  a  material  for  constructing 
artificial  dentures,  porcelain  possesses  some  disad- 
vantages, i.  e.,  there  is  some  danger  of  breakage  (out 
of  the  mouth),  it  requires  skill  to  employ  it,  and  it  is 
expensive ;  but  these  disadvantages,  not  one  of  whicli 
is  too  serious  to  be  overcome,  are  more  than  offset  by 
the  enumerated  advantages. 

The  first  disadvantage,  danger  of  breaking  a 
porcelain  denture,  will  be  reduced  to  a  minimum  if 
the  patient  will  take  the  precaution  to  place  a  towel 
or  wash-rag  in  the  basin  or  receptacle  over  which  the 
denture  is  being  cleansed.  The  second  so-called  dis- 
advantage, requirement  of  skill  on  the  part  of  the 
dentist,  can  hardly  be  allowed  if  the  dentist  will  pro- 
vide himself  with  the  proper  outfit  and  then  devote 
some  time  to  the  practice  of  manipulating  porcelain. 
Skill  on  the  part  of  the  student  and  dentist  is  re- 
quired for  the  proper  manipulation  of  porcelain,  but 
lack  of  ^kill  in  the  dentist  should  not  be  counted  as  a 
serious  disadvantage  of  porcelain  itself. 

The  third  so-called  disadvantage,  that  of  expense, 
is  not  so  much  real  as  it  is  imaginarv.    The  items  of 


PORCELAIN- — ITS   PLACE   IN    DENTISTRY  11 

time  and  platinum  constitute  the  elements  of  expense 
in  the  ''make-up"  of  a  porcelain  denture.  Both  of 
these  items  cost  more  than  the  time  and  materials 
required  for  the  construction  of  a  gold  or  rubber 
denture,  it  is  true;  but  compare  the  results,  and  you 
will  find  the  porcelain  denture  cheap  in  compari- 
son. 

"All  works  of  taste  must  bear  a  price  in  propor- 
tion to  the  skill,  taste,  time,  expense,  and  risk  attend- 
ing their  invention  and  manufacture.  Those  things 
called  dear  are,  when  justly  estimated,  the  cheapest; 
they  are  attended  with  much  less  profit  to  the  artist 
than  those  which  everybody  calls  cheap.  Beautiful 
forms  and  compositions  are  not  made  by  chance,  nor 
can  they  ever  in  any  material  be  made  at  small  ex- 
pense. A  competition  for  cheapness,  and  not  for  ex- 
cellence of  workmanship,  is  the  most  frequent  and 
certain  cause  of  the  rapid  decay  and  entire  destruc- 
tion of  arts  and  manufactures." 

If  the  dentist  will  take  the  necessary  time  and  care 
to  explain  to  his  patients  the  superiority  of  a  porce- 
lain denture  over  the  ordinary  denture  of  vulcanite, 
he  will  find  less  objection  to  expense  than  he  antici- 
pates. 

Quality  is  always  appreciated  by  an  intelligent 
public,  and  the  world  is  full  of  people  who  want  the 
best  that  skill  and  brains  can  produce.  Perhaps  the 
greatest  field  for  the  application  of  porcelain  in 
dentistry  is  in  the  construction  of  individual  crowns. 
Now  that  the  supply  houses  furnish  ready-made  com- 
pounds of  porcelain  in  a  variety  of  texture,  color, 
and  firing  point,  and  that  firing  facilities  have  been 
so  improved  as  to  permit  the  control  of  tempera- 
ture, porcelain  crown  work  has  been  placed  on  a 
practical  basis. 


12         gilbekt's  kotes  ox  dental  porcelain 

Porcelain  From  an  esthetic  and  hygienic  view-point. 
Crowns  i)orcelain  is  the  ideal  material  for  restoring 
the  lost  crowns  of  the  natnral  teeth.  Were  it  not 
for  the  third  essential  qualitication — that  of  strength 
— it  might  safely  be  claimed  that  porcelain  conld  be 
used  universally  for  the  construction  of  crowns. 

By  reason  of  their  prominent  location  in  the 
mouth,  the  six  anterior  teeth  and  the  bicuspids 
should  be  restored  with  porcelain  whenever  ]n'acti- 
cal  conditions  will  permit. 

Ready-made  crowns,  such  as  the  ''Logan"  and 
"Davis,"  are  now  obtainable  in  such  a  variety  of 
form  and  shade  as  to  indicate  their  use  either  as 
they  are  purchased  or  as  a  base  to  be  treated  to  meet 
special  requirements.  The  translucent  characteristic 
of  porcelain  indicates  its  use  in  "backing"  artificial 
facings  so  that  the  rays  of  light  may  pass  through 
the  finished  crown  and  thus  do  away  with  the  "yellow 
tint"  made  by  a  gold  backing  and  the  "gray  tint" 
made  by  a  platinum  backing.  The  hygienic  ]'>roper- 
ties  of  a  crown  are  greatly  increased  by  th«  use  of 
porcelain;  there  is  no  metallic  taste,  no  joint  to  be 
forced  open,  thus  forming  a  lodging  place  for  organic 
matter;  no  galvanic  action  can  take  place  between  a 
porcelain-backed  facing  and  the  crown  or  filling  of  an 
occluding  tooth. 

Because  the  essential  feature  of  strength  has  been 
referred  to  as  qualifying  the  universal  application 
of  porcelain  to  crown  construction,  it  is  not  to  be 
inferred  that  porcelain  does  not  possess  sufficient 
strength  to  permit  of  its  use  in  constructing  artificial 
crowns.  Where  a  sufficient  quantity  of  porcelain 
can  be  placed  back  of  a  "facing"  or  below  a  band, 
the  resultant  crown  will  be  stronger  than  a  similar 
crown  backed  with  a  metal. 


PORCELAIN ITS   PLACE   IK    DENTISTRY  13 

From  the  above  statement  it  will  be  understood 
that  the  use  of  this  material  in  crown  work  has  a 
wide  range  of  application,  but  it  is  highly  essential 
to  remember  that  it  has  its  limitations,  and  these 
limitations  must  be  respected.  In  all  cases  requiring 
artificial  crowns,  where  the  occlusion  is  such  as  to 
permit  only  a  thin  backing  or  cusp,  porcelain  is 
contraindicated. 

Great  importance  is  to  be  attached  to  the  fact 
that  the  esthetic  and  hygienic  qualities,  so  important 
to  crown  work,  are  possessed  by  porcelain,  and  it 
should  be  understood  that  when  strength  can  be  had 
in  conjunction  with  these  essential  qualities  the  ideal 
crown  can  be  constructed,  but  do  not  lose  sight  of  the 
fact  that  without  the  essential  quality  of  strength  the 
other  qualities  are  valueless.  Discriminating  judg- 
ment plays  a  very  imjDortant  role  in  porcelain  work 
of  all  kinds,  and  it  is  because  of  the  lack  of  this 
judgment  that  we  witness  failures  and  hear  extrava- 
gant assertions  relative  to  this  material. 

Any  material  which  approaches  the  ideal  to  the 
extent  which  porcelain  does  is  likely  to  be  over- 
estimated by  enthusiastic  experimenters,  and  so  it 
is  not  strange  that  we  hear  some  men  claim  that 
"porcelain  is  universally  applicable  and  is  destined 
to  supplant  gold." 

Elbert  Hubbard  says:  "The  man  who  follows 
physical  culture  as  a  business  is  as  big  a  fool  as  the 
man  who  flouts  physical  culture  entirely."  The  es- 
sence of  this  assertion  apiDlies  with  equal  force  to 
dentists  who  look  upon  porcelain  as  a  panacea. 

So  it  is  extremely  important  that  the  student 
guard  against  making  an  indiscriminate  use  of  this 
important  material  and  to  apply  it  in  its  proper 
place. 


14         gilbert's  notes  ox   dental  porcelain 

Porcelain  As  n  filling  or  inlaying  material  for  restor- 
Fillings  ing  the  lost  parts  of  the  natural  crowns, 
porcelain  has  a  good  field  of  application. 

The  necessary  appliances,  porcelains,  etc.,  have 
been  so  perfected  that  this  work  can  be  accomplislied 
without  any  of  the  disagreeable  features  which  con- 
fronted the  pioneers  in  the  use  of  this  material.  It  is 
practical  to  make  porcelain  inlays,  they  are  durable 
when  properly  made  and  located,  and  the  material 
should  certainly  be  given  a  jolace  in  the  practice  of 
every  dentist  who  cares  anything  about  the  esthetic 
side  of  his  calling.  As  in  crown  work,  discriminating 
judgment  must  be  exercised  regarding  the  applica- 
tion of  this  material — even  to  a  greater  extent  than 
in  crown  work,  for  the  strength  of  an  inlay  often 
depends  not  alone  upon  its  bulk,  but  upon  its  form 
and  position  in  relation  to  the  antagonizing  teeth. 


CHAPTER    II 


DENTAL  PORCELAINS 

Before  purchasing  an  outfit  and  undertaking  to 
make  practical  application  of  porcelain,  it  is  highly 
important  that  the  student  familiarize  himself  with 
the  fact  that  the  various  requirements  of  practice 
necessitate  a  variety  of  porcelains  to  fulfill  those 
requirements. 

Do  not  make  an  initial  mistake  by  supposing  that 
any  one  grade  of  porcelain  may  be  regarded  as  a 
''cure-all"  and  that  it  possesses  qualities  which  will 
meet  all  dental  requirements.  This  supposition  has 
been  responsible  for  many  failures  in  porcelain  work. 
A  porcelain  compound  which  has  been  especially  pre- 
pared to  meet  the  requirements  of  a  full  artificial 
denture  will  not  be  entirelj^  satisfactory  for  the  pro- 
duction of  a  small  inlay.  A  porcelain  compound  espe- 
cially prepared  to  meet  the  requirements  of  a  small 
inlay  will  not  be  entirely  suitable  for  the  production 
of  a  full  artificial  denture.  The  working  qualifica- 
tions and  the  tests  to  which  the  finished  article  must 
be  subjected  will  be  so  varied  as  to  require  com- 
pounds having  definite  characteristics  for  definite 
classes  of  work,  and  this  point  must  be  borne  in  mind 
and  freely  accepted  if  the  best  results  are  desired. 

Many  of  the  older  members  of  the  profession, 
who  in  the  years  gone  by  used  porcelain  for  the 
construction  of  artificial  teeth,  fail  to  understand 
why  their  modern  successors  desire  different  porce- 

15 


16         gilbert's  notes  on  dental  porcelain 

lain  compounds  for  the  prodnction  of  crowns  and 
inlays.  Some  of  our  present  porcelain  workers  fail 
to  understand  why  the  old  porcelain  compounds  are 
not  suitable  to  meet  present-day  requirements.  As  a 
consequence  of  this  failure  to  study  the  subject  and 
use  discriminating  judgment  regarding  the  uses  to 
which  porcelain  is  subjected,  we  hear  many  unjust 
criticisms  and  foolish  statements  which  tend  to  con- 
fuse and  prejudice  the  inexperienced. 

In  order  to  present  the  student  with  proper  data 
for  a  preliminary  study,  porcelain  compounds  will 
be  divided  into  three  classes : 


BLOCK  BODIES— HIGH-FUSING  PORCELAIN 
AND  LOAV-FUSING  PORCELAIN 

The  Three  These  three  classes  include  compounds 
Grades  which  have  been  especially  prepared  to 
meet  specific  requirements.  An  understanding  of 
said  requirements  and  the  porcelain  best  adapted  to 
fulfill  them  will  prove  of  great  value  in  deciding  just 
what  to  purchase  and  use. 

Block  The  term  Block  Bodies  has  been  used  to 

Bodies  designate    those    compounds    which   were 

largely  used  by  the  profession  before  the  advent  of 
tooth  manufacturers.  They  mav  be  defined  as  porce- 
lain compounds  which  vitrify  or  take  the  glaze  at  a 
temperature  equal  to  or  above  the  glazing  point  of 
American-made  artificial  teeth. 

Compounds  similar  in  nature  to  these  so-called 
Block  Bodies  are  now  used  by  the  manufacturers  of 
artificial  teeth  and  also  by  some  practitioners  of  den- 
tistry who  prefer  to  carve  and  fire  their  own  artificial 


DENTAL     PORCELAINS  17 

teeth  rather  than  accept  the  factory-made  teeth  of  the 
manufacturer.  The  compounds  which  are  suitable 
for  the  carving  of  teeth  are  entirely  different  in  char- 
acter from  the  compounds  which  are  now  popular 
with  the  profession  and  which  are  being  used  in  the 
construction  of  crowns  and  inlays. 

The  chief  difference  between  the  old-line  porce- 
lains and  the  porcelains  of  today  is  in  the  firing  or 
glazing  point.  Other  points  of  difference  exist  be- 
tween the  compounds,  but  they  are  not  so  marked  as 
is  the  firing  point. 

It  should  be  understood  that  Block  Bodies  were 
in  vogue  before  the  appearance  of  the  electric  fur- 
naces and  many  of  the  gas  and  oil  furnaces  which 
we  have  at  the  present  time. 

Under  the  old  firing  conditions  a  dentist  was 
obliged  to  use  a  furnace  made  of  fire-clay,  built  in 
sections  which  were  held  together  by  iron  bands. 
Coal  was  the  source  of  heat,  and  by  its  use  very  high 
temperatures  could  be  produced.  It  should  also  be 
remembered  that  block  bodies  were  used  before  the 
manufacturers  of  artificial  teeth  provided  the  great 
variet}^  of  forms  and  shades  which  they  now  manu- 
facture and  carry  in  stock  ready  for  selection  and 
application  by  the  dentist. 

The  advent  of  the  modern  artificial  tooth  is  re- 
sponsible for  the  discontinuance  of  old  hand-carved 
methods  of  producing  teeth,  and  as  a  natural  conse- 
quence block  bodies  have  largely  been  discarded. 
For  the  jjurposes  intended  these  block  bodies  were 
essential  to  the  desired  results;  a  porcelain  having 
a  high  firing  point  was  as  much  a  necessity  in 
producing  teeth  by  the  hand-carved  method  as  it  is 
today  in  producing  teeth  by  the  molding  methods  of 
the  modern  tooth  manufacturers. 


18  GILBERT ''S    NOTES    OK    DENTAL    PORCELAIN 

The  Use  of  To  those  members  of  the  profession  who 
Block  Body  are  not  satisfied  with  the  artificial  teeth 
produced  in  the  factories  of  the  manufacturers  and 
to  those  who  possess  the  knowledge  and  skill  neces- 
saiy  to  i3roduce  a  better  product  in  their  own  labo- 
ratories by  their  own  hands,  the  so-called  ''block 
bodies"  are  recommended. 

The  employment  of  block  bodies  will  require  a 
furnace  especially  made  for  obtaining  and  maintain- 
ing very  high  temperature.  Do  not  be  deceived  by 
any  statements  to  the  effect  that  the' present  type  of 
electric  furnaces  can  be  depended  upon  to  fire  large 
cases  made  of  block  body.  It  is  true  that  some  of 
the  bodies  having  an  extremely  high  firing  point  can 
be  glazed  in  the  electric  furnace ;  but  this  fact  should 
be  accepted  only  with  the  understanding  that  while 
this  high  temperature  can  be  obtained  and  maintained 
for  a  short  time,  it  is  not  practical  to  subject  the  plati- 
num wire  of  an  electric  furnace  to  any  such  strain. 
The  only  furnaces  which  can  be  recommended  for 
obtaining  and  maintaining  practical  temperatures  for 
this  class  of  work  will  be  found  described  under  the 
chapter  on  "Furnaces." 


HIGH-FUSING  PORCELAINS 

The  term  "High-Fusing"  is  relative  rather  than 
definite,  but  it  seems  to  have  been  accepted  by  the 
profession  to  mean  a  porcelain  which  vitrifies  or 
takes  the  glaze  at  a  temperature  higher  than  the 
melting  point  of  pure  gold.  Such  a  definition  means 
nothing  so  far  as  composition  or  general  character- 
istics of  the  porcelain  is  concerned.  The  words 
"High-Fusing"  are  simply  relative  as  to  the  firing 


DENTAL,     PORCELAINS  19 

point,  and  are  used  to  distinguish  this  grade  of  porce- 
lain from  the  "Low-Fusing"  porcelains  or  those 
which  vitrify  or  take  the  glaze  at  a  temperature 
lower  than  the  melting  point  of  pure  gold. 

According  to  the  definition  given  above,  the  ex- 
tremely high-fusing  porcelains,  or  those  which  have 
been  described  as  block  bodies,  are  included  under 
the  term  high-fusing. 

High-Fusing  In  Order  to  make  the  term  a  little  more 
Porcelain  comprehensive  to  the  student,  the  generally 
accepted  definition  of  "High-Fusing"  will  be  modi- 
fied to  read  as  follows  :  A  porcelain  which  vitrifies  or 
takes  the  glaze  at  a  temperature  somewhere  between 
the  melting  point  of  pure  gold  and  the  glazing  point 
of  an  American-made  porcelain  tooth.  Under  the 
latter  definition  can  be  classed  most  of  the  porcelain 
compounds  which  the  profession  is  using  for  the 
construction  of  continuous-gum  dentures,  crowns, 
bridges,  and  inlays. 

While  there  are  many  compounds  of.  porcelain 
which  are  classified  under  the  general  term  of  "High- 
Fusing,"  it  is  important  to  remember  that  no  two 
of  these  compounds  are  alike  except  in  name. 

Each  manufacturer  of  dental  porcelain  has  char- 
acterized his  product  by  some  peculiarity  in  formula 
or  in  method  of  preparation,  so  that  while  their  vari- 
ous fusing  points  have  placed  most  of  them  under 
the  definition  of  the  term  "High-Fusing,"  their  indi- 
vidual working  and  physical  characteristics  call  for 
recognition  as  individual  porcelains. 

The  best  and  in  fact  the  only  way  foi-  the  student 
in  porcelain  work  to  become  familiar  with  the  charac- 
teristics of  the  different  porcelains  is  to  supply  him- 
self with  a  small  quantity  of  each,  and  with  them  make 
the  necessary  laboratory  or  clinical  experiments. 


20         gilbert's  notes  on  dental,  porcelain 

The  Use  of  ^'^r  the  construction  of  artificial  crowns 
High-Fusing  and  inlays,  porcelain  compounds  of  the 
Porcelain  high-fusing  variety  are  recommended,  and 
if  it  is  this  class  of  porcelain  work  which  the  student 
desires  to  pursue,  he  will  do  well  to  purchase  samples 
of  this  grade  of  porcelain  and  experiment  until  he 
finds  the  special  compound  best  suited  to  meet  his 
individual  requirements. 


LOW-FUSING  PORCELAINS 

Low-Fusing  This  term  is  generally  accepted  to  mean 
Porcelain  porcelain  compounds  which  vitrify  or  take 
the  glaze  at  a  temperature  below  the  melting  point 
of  pure  gold. 

This  definition  is  subject  to  the  same  remarks  as 
have  been  given  in  reference  to  the  term  High- 
Fusing;  that  is,  while  there  are  several  compounds 
of  porcelain  classified  under  the  term  Low-Fusing, 
it  is  important  to  remember  that  no  two  of  these 
compounds  are  alike  except  in  name.  In  the  effort 
to  produce  a  porcelain  whose  firing  temperature 
would  be  lower  than  the  melting  point  of  pure 
gold,  each  manufacturer  has  produced  a  material 
having  peculiar  characteristics,  and  these  character- 
istics must  be  understood  before  a  selection  can  in- 
telligently be  made. 

For  the  construction  of  certain  classes  of  inlays, 
the  Low-Fusing  porcelains  may  be  employed,  but  their 
range  of  adaptability  is  to  a  great  extent  limited  by 
the  nature  of  their  working  qualities  and  the  skill 
of  the  dentist. 

The  firing  conditions  at  the  disposal  of  the  stu- 


DENTAL     PORCELAINS  21 

dent  will,  in  a  manner,  influence  many  in  their  selec- 
tion of  a  dental  porcelain.  In  localities  where  the 
electric  current  is  not  obtainable,  and  the  use  of  gaso- 
line and  fuel  oil  is  prohibited,  gas  becomes  the  only 
means  of  firing  porcelain.  Under  this  condition  there 
is  little  choice  to  be  made,  and,  as  a  consequence,  the 
Low-Fusing  porcelains  which  will  vitrify  or  take  the 
glaze  at  a  temperature  obtainable  by  the  ordinary 
gas  blowpipe  must  be  selected. 


CHAPTEE   III 


LABORATORY  EXPERIMENTS 

Certain  laboratory  experiments  with  the  various 
porcelain  compounds  now  available  will  prove  of 
great  value  to  either  student  or  practitioner.  If  the 
characteristic  working  qualities,  firing  point,  amount 
of  shi'inkage,  strength,  stability  of  color,  etc.,  of  the 
different  porcelains  are  understood,  it  will  be  an  easy 
matter  to  select  that  compound  which  meets  indi- 
vidual requirements,  and  in  this  way  much  time, 
worry,  and  expense  may  be  saved. 

Fig.  1 


A  simple  yet  an  effective  method  of  testing  the 
qualities  of  a  porcelain  will  be  found  in  pursuing  the 
following  plan:  Make  an  outfit  consisting  of  an  ab- 
sorbing block  and  a  small  brass  form.  The  absorbing 
block  should  be  of  plaster,  and  it  can  be  easily  made 
by  mixing  plaster  rather  thick  and  pouring  the  same 
into  a  discarded  box-lid  or  anything  which  will  give 
the  block  form  and  permit  of  a  level  surface.  (Fig.  1.) 

22 


LABORATORY     EXPERIMENTS  23 

The  brass  form  should  be  made  in  two  parts,  each 
part  consisting  of  one  end  and  one  side.     (Fig.  2.) 

Fig.  2 


Such  a  form  will  permit  of  adjustment  and  pro- 
vide a  means  for  making  porcelain  blocks  of  many 
sizes.     (Fig.  3.)     The  plaster  block  is  used  for  the 


Fig.  3 


purpose  of  absorbing  water  from  the  mixed  porce- 
lain. 

With  this  simple  outfit  and  samples  of  porcelain 
it  is  possible  to  conduct  a  series  of  experiments 
which  will  show  comparative  qualities  of  firing  point, 
shrinkage,  color  stability,  and  capabilities  of  contour. 
In  order  to  place  the  different  compounds  under 
test  on  an  equal  basis,  the  little  form  should  be 
marked  so  that  all  the  blocks  will  be  of  uniform  shape 
and  size.  Before  using  the  form  it  and  that  por- 
tion of  the  plaster  block  on  which  the  porcelain  is  to 
be  poured  or  packed  should  be  wiped  clean  and 
slightly  oiled. 

Place  the  oiled  form  on  the  absorbing  block,  mix 
the  porcelain  to  the  desired  consistence  on  a  clean 
glass  slab,  and  then,  holding  the  form  in  place  with  the 


24  GILBERT ""s    NOTES    ON    DENTAL    PORCELAIN 

index  finger  and  thumb  of  the  left  hand,  pack  or 
pour  the  porcelain  into  the  form  with  a  spatula  held 
in  the  right  hand.  Allow  the  porcelain  to  set,  level 
the  surface  with  a  knife  or  spatula,  and  with  the  index 
finger  and  thumb  of  both  hands  give  the  form  and 
porcelain  a  downward  and  outward  pressure,  thus 
separating  the  porcelain  block  from  the  plaster,  after 
which  the  parts  of  the  form  can  be  slid  apart  and  the 
test  piece  laid  aside,  dried,  and  placed  on  a  slide 
ready  for  the  furnace.    ( Fig.  4. ) 

Fig.  4 


Test  for  Shrinkage  of  any  porcelain  will,  to  some 
Shrinkage  extent,  be  dependent  upon  the  character  of 
the  mix.  If  the  porcelain  is  mixed  with  water  to  a 
point  similar  to  the  consistence  of  thick  cream,  the 
fired  piece  will  show  a  greater  shrinkage  than  will  a 
piece  in  which  the  mix  was  of  a  consistence  similar 
to  putty.  In  making  comparative  tests  of  the  differ- 
ent porcelains,  the  above  point  must  be  observed,  and 
each  grade  of  material  should  be  worked  in  a  uni- 
form manner. 

Test  for  In  testing  the  firing  or  glazing  point  of  a 
Glazing  Point  porcelain  compound,  the  student  may  wish 
to  ascertain  the  time  required  by  a  given  furnace, 
or  he  may  wish  to  know  how  the  firing  point  of  one 
compound  compares  with  the  firing  point  of  another. 
In  either  case  the  little  test  pieces  will  prove  of 
more  value  than  will  any  temperature  table  pur- 
porting to  give  the  firing  points  of  different  porce- 
lains in  degrees  Fahrenheit. 


LABORATORY  EXPERIMENTS  25 

Author's  An  experiment  made  by  the  author  will 
Experiment  give  an  excellent  understanding  of  the  dif- 
ferences in  firing  point  between  ten  of  the  well-known 
porcelain  compounds.  There  is  no  other  way  of  in- 
telligently designating  these  porcelains  except  by  the 
name  of  the  manufacturer,  and  as  nothing  of  a  preju- 
dicial character  will  be  said,  there  can  be  no  objection 
on  the  part  of  those  who  prejDare  the  porcelains. 


TEST  FOR  RELATIVE  FIRING  POINT 

The  porcelains  under  test  were  as  follows : 

The  Jenkins  Porcelain  Enamel. 

C.  Ash  &  Sons'  Low-Fusing  Porcelain. 

C.  Ash  &  Sons '  High-Fusing  Porcelain. 

The  S.  S.  White  Co.'s  Medium-Fusing  Porcelain. 

The  Consolidated  Co.'s  High-Fusing  Porcelain. 

Brewster's  Enamel  Body. 

Brewster's  Foundation  Body. 

The  S.  S.  White  Co.'s  High-Fusing  Porcelain. 

S.  L.  Close's  Body. 

Allen's  Body  (S.  S.  White  Co.'s  make). 

In  order  to  place  each  porcelain  upon  equal  foot- 
ing, a  mold  was  constructed  (Fig.  5)  for  the  purpose 
of  making  test  cones,  and  a  second  mold,  such  as 
shown  in  Fig.  6,  was  made  for  producing  a  slab  of 
porcelain  which  would  hold  the  test  cones  while  they 
were  being  fired.  By  making  these  test  cones  all  in 
the  same  mold,  a  uniform  size  and  form  was  assured. 

In  the  slab  mold,  ten  forms  were  made  from  The 
S.  S.  White  Co.'s  High-Fusing  Porcelain,  and  in  the 
cone  mold,  ten  cones  from  each  of  the  porcelains 


26 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


above  designated.  Upon  each  of  the  molded  slabs  a 
cone  of.  each  of  the  porcelains  was  set,  care  being 
taken  to  place  them  in  the  same  relative  order  On 
all  of  the  slabs.  There  were  thus  constructed  ten  test 
pieces,  so  arranged  that  comparison  of  results  should 

Fig.  5 


Fig.  6 


be  easy.  These  test  pieces  were  then  fired,  one  after 
the  other,  exposing  all  to  the  furnace  heat  under 
as  nearly  as  possible  the  same  conditions. 

The  first  was  removed  from  the  muffle  as  soon  as 
the  characteristic  glaze  appeared  on  the  material 
having  the  lowest  firing  point,  the  second,  when 
the  glaze  appeared  on  the  next  higher-fusing  porce- 
lain;   and    so    on    through    the    entire    lot.    each 


LABORATORY     EXPERIMENTS 


27 


showing  the  firing  point  of  one  particular  porce- 
lain together  with  the  effect  of  that  tempera- 
ture on  all  the  others.  At  the  end  of  the  experi- 
ment we  had  a  clear  indication  of  the  relative  firing 
point  of  all  the  porcelains  under  test.  The  result 
of  each  test  piece  should  be  seen  to  be  appreciated, 
for  the  test  not  only  shows  the  relative  firing  point 
of  each  porcelain  compound,  but  it  gives  an  excellent 
idea  of  the  amount  of  shrinkage  in  each  grade  of 
porcelain,  and  it  shows  conclusively  the  amount  of 
abuse  which  each  compound  will  stand,  the  capabili- 
ties of  contour,  and  stability  of  color. 

It  is  impossible  to  portray  all  these  results  upon 
paper,  but  the  relative  firing  point  of  the  ten  porce- 
lains can  be  shown  by  the  following  illustrations : 

Fig.  7  illustrates  the  condition  of  the  ten  cones 
before  they  were  placed  in  the  furnace. 

Fig.  7 


A  A  /^  /^ 


\\  ,    -/ 


Fig.  8  illustrates  the  condition  of  the  cones  after 

Fig.  8 


the  porcelain  having  the  lowest  firing  point   (Jen- 
kins 's)  took  the  glaze.    The  temperature  necessary  to 


28 


GILBERT'S    NOTES    ON    DENTAL    PORCELAIN 


glaze  the  Jenkins  porcelain  did  not  glaze  Ash's  Low- 
Fusing  Porcelain,  although  it  caused  some  shrinkage 
in  both  Ash's  Low  and  Ash's  High.  No  appreciable 
effect  was  made  upon  any  of  the  other  seven  porce- 
lains. 

Fig.  9  illustrates  the  condition  of  the  cones  after 


Fig.  9 


the  porcelain  having  the  second  higher  firing  point 
(Ash's  Low-Fusing)  took  the  glaze.  The  temperature 
necessary  to  glaze  Ash's  Low-Fusing  Porcelain  over- 
fired  Jenkins's  to  the  extent  shown,  caused  shrink- 
age of  Ash's  High-Fusing  Porcelain,  The  S.  S.  White 
Co.'s  Medium-Fusing,  and  the  Consolidated  Co.'s 
High-Fusing,  but  had  little  appreciable  effect  upon 
the  Brewster  Enamel,  Brewster  Foundation,  S.  S. 
White  Co.'s  High-Fusing,  Close's  Body,  and  Allen's 
Body. 

Fig.  10  illustrates  the  condition  of  the  cones  after 

Fig.  10 


the  porcelain  having  the  third  higher  firing  point 
(Ash's  High-Fusing)  took  the  glaze.  This  test  shows 
that  the  temperature  necessary  to  glaze  Ash's  High- 


LABORATORY     EXPERIMENTS 


29 


Fusing  Porcelain  overfires  both  the  Jenkins  and 
Ash's  Low-Fusing  to  the  extent  shown,  partially 
glazes  The  S.  S.  White  Co.'s  Medium-Fusing,  Con- 
solidated Co.'s  High-Fusing,  Brewster's  Enamel,  and 
effects  the  shrinkage  of  Brewster's  Foundation,  S.  S. 
White  Co.'s  High-Fusing,  Close's  Body,  and  Allen's 
Body. 

Fig.  11  illustrates  the  condition  of  the  cones  after 

Fig.   11 


the  porcelain  having  the  fourth  higher  firing  point 
(S.  S.  White  Co.'s  Medium-Fusing)  took  the  glaze. 

The  temperature  necessary  to  glaze  The  S.  S. 
White  Co.'s  Medium-Fusing  Porcelain  overfires  Jen- 
kins's, Ash's  Low- Fusing,  and  Ash's  High-Fusing  to 
the  extent  shown;  it  also  increases  the  glaze  of  the 
Consolidated  Co.'s  High-Fusing,  Brewster's  Enamel, 
partially  glazes  Brewster's  Foundation,  The  S.  S. 
White  Co.'s  High-Fusing,  Close's  Body,  and  hard 
biscuits  the  Allen  Bodj 

Fig.  12  illustrates  the  condition  of  the  cones  after 

EiG.  12 


the  porcelain  having  the  fifth  higher  firing  point 
(Consolidated  Co.'s  High-Fusing)    took  the  glaze. 


30.       gilbert's  notes  on  dental  porcelain 

Tlie  temperature  required  to  properly  glaze  this 
])orcelain  overfires  Jenkins's,  Ash's  Low-Fusing, 
Ash's  High-Fusing  to  the  extent  shown ;  very  slightly 
overglazes  The  S.  S.  White  Co.'s  Medium-Fusing, 
about  glazes  Brewster's  Enamel,  and' increases  the 
glaze  of  Brewster's  Foundation,  The  S.  S.  White 
Co.'s  High-Fusing,  the  Close  and  Allen  Bodies.  (The 
S.  S.  White  Co.'s  Medium-Fusing  and  the  Consoli- 
dated Co.'s  High-Fusing  have  practically  the  same 
firing  point.) 

Since  this  experiment  was  made  the  Consolidated 
Dental  Mfg.  Co.  have  marketed  a  new  product  which 
has  a  glazing  point  considerably  higher  than  the 
porcelain  first  made  by  them.  The  glazing  point  of 
their  present  grade  of  porcelain  is  higher  than  the 
glazing  point  of  Allen's  Body.  The  difference  in 
glazing  point  between  the  Consolidated  Company's 
High-Fusing  Porcelain  and  Allen's  Body  is  shown  in 
Fig.    13.      The    temperature    required   to    properly 

Fig.  13 


glaze  the  Consolidated  Dental  Mfg.  Co.'s  High-Fus- 
ing Porcelain  overfires  the  Allen  Body  to  the  extent 
shown.  The  effect  which  this  temperature  would 
have  upon  the  other  nine  porcelains  will  be  left  to 
the  imagination. 

Fig.  14  illustrates  the  condition  of  the  cones  after 
the  porcelain  having  the  sixth  higher  firing  point 
(Brewster's  Enamel)  took  the  glaze.    The  tempera- 


LABORATORY     EXPERIMENTS 


31 


ture  required  to  glaze  Brewster's  Enamel  overtired 
Jenkins's,  Ash's  Low,  Ash's  High,  S.  S.  AVhite  Co.'s 


Fig.  14 


Medium,  and  Consolidated  Co.'s  to  the  extent  shown, 
and  took  practically  all  the  shrinkage  from  the  Brew- 
ster Foundation,  S.  S.  White  Co.'s  High,  Close,  and 
Allen  Bodies. 

Fig.  15  illustrates  the  condition  of  the  cones  after 
the  porcelain  having  the  seventh  higher  firing  point 

Fig.  15 


(S.  S.  White  Co.'s  High-Fusing  Porcelain)  took  the 
glaze.  The  temperature  required  to  properly  glaze 
this  porcelain  overfired  the  Jenkins,  Ash's  Low- 
Fusing,  Ash's  High-Fusing,  S.  S.  White  Co.'s  Me- 
dium, Consolidated  Co.'s  High-Fusing,  and  Brew- 
ster's Enamel  to  the  extent  shown;  closely  approxi- 
mated the  proper  glaze  of  the  Brewster  Foundation, 
the  Close  and  Allen  Bodies.  (This  test  clearly 
demonstrated  that  the  firing  point  of  The  S.  S. 
White  Co.'s  High-Fusing  Porcelain,  Brewster's 
Foundation  Porcelain,  and  Close's  Body  are  approxi- 
mately the  same.) 


32         gilbert's  notes  on  dental  porcelain 

Fig.  16  illustrates  the  condition  of  the  cones  after 
the  porcelain  having  the  eighth  higher  firing  point 
(Brewster's  Foundation)  took  the  glaze.  The  tem- 
perature required  to  properly  glaze  the  Brewster 


Fig.   Ifi 


Foundation  overtired  the  Jenkins,  Ash's  Low  and 
Ash's  High-Fusing,  The  S.  S.  White  Co.'s  Medium, 
The  Consolidated  Co.'s  High-Fusing,  Brewster's 
Enamel,  and  The  S.  S.  White  Co.'s  High-Fusing  to 
the  extent  shown.  (This  test  again  shows  that  the 
firing  point  of  The  S.  S.  White  Co.'s  High-Fusing 
Porcelain,  Brewster's  Foundation,  and  Close's  Body 
are  approximately  the  same.) 

Fig.  17 


Fig.  17  illustrates  the  condition  of  the  cones  after 
the  porcelain  having  the  ninth  higher  firing  point 
(Close's  Body)  took  the  glaze.  (This  test  showed 
practically  the  same  result  as  the  two  previous  tests, 
and  again  proved  that  The  S.  S.  White  Co.'s  High- 
Fusing  Porcelain,  Brewster's  Foundation  Porcelain, 
and  Close's  Body  are  practically  alike  as  far  as  firing 
point  is  concerned.) 


LABORATORY     EXPERIMENTS  33 

Fig.  18  illustrates  the  condition  of  the  cones  after 
the  porcelain  having  the  tenth  higher  firing  point 
(Allen's  Body)  took  the  glaze.  The  temperature 
required  to  properly  glaze  Allen's  Body  overfires  all 
the  other  porcelains  to  the  extent  shown. 

Fig.  18 


The  practical  relative  firing  point  of  these  ten 
porcelains  is  clearly  shown  in  the  above  tests,  and  the 
result  gives  the  student  a  much  better  conception  of 
the  temperature  required  to  glaze  a  given  porcelain 
than  can  be  gained  from  a  table  purporting  to  show 
the  firing  point  of  the  different  porcelains  in  degrees 
Fahrenheit. 

Pyrometers,  which  are  practical  instruments  for 
determining  the  definite  temperatures  at  which  a 
given  porcelain  compound  takes  a  certain  degree  of 
glaze,  can  be  depended  upon  to  show  the  relative 
difference  in  the  glazing  point  of  the  various  porce- 
lains; but  no  device  showing  this  difference  in  cold 
type  only  can  instruct  the  "worker"  like  the  test 
detailed  above. 

Test  for  For  practical  application  in  crown  work 
Contouring  ^^^  jj^  many  classes  of  inlay  work  it  is 
and  Color  essential  that  the  porcelain  be  capable  of 
Stability  maintaining  a  desired  form  during  the  fir- 
ing process. 

AVell-defined  cusps  and  sulci  are  a  necessity  in 
crown  construction  to  restore  the  utilitarian  needs  of 
mastication,  and  well-defined  lines  of  contour  and 

3 


34         gilbert's  notes  on  dental  porcelain 

contact  are  a  necessity  in  inlay  construction  for  re- 
storing the  hygienic  and  esthetic  requirements. 

Stability  of  color  is  another  essential  quality  of  a 
dental  porcelain,  and  it  is  desirable  that  this  quality 
be  present  to  a  marked  degree.  There  is  a  great 
difference  exhibited  by  the  various  compounds  when 
practically  tested  for  either  of  the  above  qualities. 
Some  of  them  must  be  treated  with  great  care  in 
the  mixing  and  must  be  watched  very  closely  while 
in  the  furnace,  in  order  to  insure  contour  and  color ; 
while  others  do  not  require  such  detailed  care  in 
the  mixing,  and  they  can' be  left  in  the  furnace  for 
a  limited  time  beyond  the  actual  time  required  to 
glaze  them  without  any  practical  change  occurring 
in  either  contour  or  color.  This  difference  in  practical 
working  qualities  is  one  which  should  be  thoroughly 
understood  by  the  student,  for  it  has  an  important 
bearing  upon  all  porcelain  constructions. 

Either  of  the  tests  for  shrinkage  or  firing  point, 
previously  outlined,  will  afford  a  ready  means  of 
determining  to  what  extent  each  compound  of  porce- 
lain possesses  the  capabilities  of  maintaining  con- 
tour and  color;  but  another  easy  method  is  to  cut  a 
triangular  groove  in  a  piece  of  metal  (Fig.  19),  and 
in  this  groove  pack  a  little  of  the  mixed  jDowder  to 
be  tested.  This  will  produce  a  little  triangular 
pyramid,  having  three  well-defined  lines  running 
to  a  common  point,  and  it  will  make  a  good  test  piece 
upon  which  to  try  the  effect  of  temperatures. 

The  effect  of  heat  upon  these  little  test  pieces  will 
give  an  excellent  idea  of  what  may  be  expected  in 
the  practical  firing  of  inlays  and  crowns.  Some  of 
the  porcelain  compounds  require  great  care  in  the 
firing  in  order  to  make  them  hold  their  color  and 
maintain  the  sharp  lines  and  points;  there  is  a  ten- 


LABORATORY     EXPERIMEXTS 


35 


dency  to.  assume  a  spheroidal  form  when  subjected 
to  only  a  slight  excess  of  temperature.  Others  re- 
quire less  care  in  the  firing  in  order  to  produce  the 
proper  color  and  contour,  and  a  considerable  excess 

Fig.  19 


of  temperature  will  be  endured  without  any  prac- 
tical effect.  To  illustrate  this  point:  When  placed 
in  the  furnace  a  piece  of  porcelain  has  this  form 
(Fig.  20) ;  the  slightest  excess  of  temperature  has  the 
effect  of  instantly  changing  it  to  this  form  (Fig,  21) ; 
another  piece  when  placed  in  the  furnace  has  the 
same  form  as  the  first  (Fig.  20),  but  made  of  a  differ- 

FiG.  20  Fig.  21  Fig.  22 


ent  grade  of  porcelain.  A  considerable  excess  of 
temperature  has  no  appreciable  effect  upon  its  form 
or  color  and  there  is  little  tendency  for  it  to  assume 
a  spheroidal  shape.  (Fig.  22.)  The  difference  in  these 
porcelains  is  all  in  favor  of  the  latter  grade,  for  it 
permits  of  more  or  less  abuse  and  does  not  require 
the  skill  of  an  expert  to  obtain  satisfactory  results. 

A  porcelain  which  has  a  tendency  to  assume  a 
spheroidal  form  upon  receiving  a  slight  excess  of 
heat  will  also  have  a  tendency  to  bleach  or  lose  color ; 
especially  is  this  so  where  the  edges  of  an  inlay  are 
sharp  and  well  defined. 


CHAPTER   IV 


PRACTICAL  APPLICATION  OF  BLOCK  BODIES 

Former  A  half -century  ago  dentists  were  obliged 
Conditions  to  prepare  their  own  porcelain  compounds, 
carve  and  fire  the  same  into  tooth  forms,  just  as 
they  were  obliged  to  refine  and  roll  to  gage  their 
gold  plate  and  solders.  Modern  conditions  have 
changed  matters  to  such  an  extent  that  many  necessi- 
ties of  the  past  are  found  as  conveniences  of  the 
present,  and,  as  stated  in  a  previous  chapter,  the 
large  assortment  of  ready-made  teeth  provided  by 
the  manufacturer  has  relegated  block  bodies  to  the 
use  of  the  isolated  specialists  who  think  they  can 
carve  teeth  better  than  the  manufacturer  can  mold 
them.  The  ordinary  practitioner  of  today  might 
spend  years  in  carving  and  manipulating  porcelain 
into  tooth  forms  only  to  produce  in  the  end  poor 
imitations  of  teeth  which  can  be  secured  in  the 
supply  houses  for  a  small  expenditure  of  time  and 
money.  While  all  the  above  is  true,  and  while  it 
demonstrates  the  fact  that  practically  all  of  the  arti- 
ficial teeth  used  by  dentists  are  products  of  the  manu- 
facturer, nevertheless  there  is  a  field  for  the  applica- 
tion of  block  bodies  by  the  dental  artist. 

Unless  the  student  or  practitioner  has  peculiar 
talent  for  this  kind  of  work,  and  unless  he  is  willing 
to  provide  himself  with  the  necessary  firing  facilities 
and  to  devote  much  of  his  time  to  the  compounding 
of  porcelain  and  practice  of  manipulating  the  same, 

36 


PKACTICAL    APPLICATIOInT    OF    BLOCK    BODIES  37 

he  will  do  well  to  give  up  all  thought  of  employing 
block  bodies  and  rest  content  either  with  teeth  as 
they  are  made  by  the  manufacturer  or  else  be  content 
to  have  the  specialist  in  ''carved  work"  make  teeth 
for  him. 

If  the  student  or  practitioner  has  genius  in  this 
direction,  and  is  willing  to  provide  himself  with  the 
necessary  firing  facilities  and  is  ready  to  devote  much 
time  to  the  practice  of  making  hand-carved  teeth,  he 
may  develop  a  skill  which  will  enable  him  to  produce 
teeth  for  special  cases  which  will  prove  superior  to 
anything  which  is  "ready  made." 
Qualities  Re-  Before  outlining  the  technic  of  making 
quired  in  teeth  by  hand  it  will  be  well  to  devote 
Block  Body  g^jj^e  time  to  a  description  of  the  qualities 
which  the  porcelain  compound,  suitable  for  this  class 
of  work,  must  possess.  Briefly  stated,  a  porcelain 
suitable  for  the  production  of  hand-carved  artificial 
teeth  must  be  plastic  enough  to  permit  of  carving 
and  have  no  tendency  to  flake  or  crumble.  It  must, 
when  fired,  possess  strength  enough  to  withstand  all 
manipulations  necessary  to  attach  it  to  the  base  (sol- 
dering, vulcanization,  etc.),  strength  enough  to  with- 
stand all  practical  strain  when  in  the  mouth ;  it  must 
be  natural  in  physical  appearance  and  capable  of 
withstanding  all  action  of  oral  secretions. 

The  essential  qualities  above  enumerated  are  so 
widely  different  in  character  that  it  is  impossible  to 
find  all  of  them  embodied  in  one  grade  of  porcelain, 
and  for  that  reason  it  is  necessary  to  use  a  ''body" 
which  will  give  the  essentials  of  plasticity,  form,  and 
The  Lack  strengtli,  and  an  enamel  which  will  give  the 
of  Demand  essentials  of  naturalness,  which  includes 
translucency,  shade,  etc.  Owing  to  the  fact  that  prac- 
tically all  dentists  rely  upon  tlie  manufacturer  for 


38         gilbert's  kotes  on  dental  porcelain 

their  supply  of  artificial  teeth,  and  to  the  fact  that 
there  is  very  little  use  for  block  bodies  outside  of 
tooth-making,  there  is  little  or  no  commercial  de- 
mand for  the  same,  and  so  the  dentist  who  takes  up 
this  class  of  work  is  compelled  to  compound  his  own 
porcelains  or  else  place  special  orders  with  the  suji- 
ply  houses. 

The  preparation  of  the  basal  materials  entering 
into  the  composition  of  dental  porcelains,  the  com- 
pounding of  the  prepared  materials,  and  the  variety 
which  must  be  made  in  order  to  meet  all  practical 
requirements  is  a  business  of  itself,  and  the  busy 
dentist  will  soon  appreciate  this  fact  if  he  undertakes 
to  make  his  own  compounds. 

Formulas  for  making  block  bodies  and  enamels 
could  be  given  in  unlimited  number,  according  to 
peculiar  working  qualities  desired  and  the  variety  of 
color  necessary  to  meet  all  dental  requirements. 
Making  Owing  to  the  fact  that  each  of  the  raw  ma- 
Porcelain  terials  entering  into  the  composition  of  den- 
Compounds  ^^1  porcelains  varies  greatly  in  character,  it 
seems  unwise  to  give  definite  proportions  with  any 
sort  of  guarantee  that  a  definite  result  can  be  pro- 
duced. By  this  is  meant  that  a  formula  printed  in  this 
book,  read  by  dentists  in  all  sections  of  the  country, 
compounded  from  raw  materials  picked  up  locally  by 
the  persons  working  the  compound,  would  result  in 
the  production  of  ' '  bodies ' '  widely  different  in  char- 
acter. Generally  speaking,  a  practically  infusible 
grade  of  silex  is  used  to  maintain  form,  kaolin  to 
impart  strength  and  plasticity,  feldspar  to  produce 
the  necessary  glazing  and  translucency,  and  the 
oxides  of  metals  to  give  the  various  coloring  effects. 

If  all  silex,  all  kaolin,  and  all  feldspar  were  alike 
in  character,  it  would  be  an  easy  matter  to  recom- 


PRACTICAL    APPLICATION    OF    BLOCK    BODIES  39 

mend  definite  proportions  of  each  for  the  production 
of  definite  results ;  but  such  is  not  the  case,  and  there- 
fore little  or  no  reliance  can  be  placed  in  formulas 
generally  found  in  text-books.  If  the  reader  desires 
to  manufacture  "block  bodies,"  there  is  only  one 
satisfactory  way  to  do  it,  and  that  way  is  to  test  all 
the  varieties  of  the  raw  materials  he  can  find,  select 
the  variety  of  each  best  suited  to  his  needs,  and 
compound  them  in  varying  proportions  and  by  differ- 
ent methods  until  the  desired  result  is  obtained,  keep- 
ing careful  record  of  each  experiment  as  made. 
Practical  Ap-  The  technic  of  making  an  artificial  tooth 
plication  of  by  hand  may  be  described  as  follows:  A 
Block  Bodies  p] aster  impression  of  the  adjoining  and  oc- 
cluding teeth,  and  models  from  the  same  are  made  in 
the  usual  way.  The  models  should  be  thoroughly 
varnished  and  then  oiled  slightly,  preferably  with 
olive  oil,  in  order  to  permit  the  easy  removal  of  the 
porcelain  after  the  carving  has  been  done. 

The  body  can  be  mixed  first  upon  a  porcelain  or 
glass  slab  and  then  in  the  palm  of  the  hand,  work- 
ing it  with  a  bone  spatula  or  the  fingers  until  it  is 
free  from  air  bubbles  and  of  a  consistence  similar  to 
putty.  Take  enough  of  the  mixed  body  to  fill  the 
edentulous  space,  and  with  a  suitable  carving  tool 
carve  the  body  to  the  desired  shape,  making  allow- 
ance for  shrinkage,  which  should  be  about  20  per  cent. 
The  amount  of  shrinkage  and  strength  of  the  finished 
tooth  will  depend  greatly  upon  the  amount  of  water 
which  is  in  the  putty-like  mixture  and  the  manner  in 
which  it  is  used  during  the  carving.  In  order  to 
secure  the  minimum  amount  of  shrinkage,  the  mixture 
should  be  as  dry  as  it  is  practical  to  work  it  and  it 
should  be  condensed  as  much  as  possible.  In  order 
to  work  the  body  fairly  stiff  without  causing  "dry 


■iO         gilbert's  notes  on  dental  porcelain 

cracks"  and  rough  places,  it  is  good  j^ractice  to  press 
the  body  in  place  as  much  as  possible  with  the  fingers 
and  proceed  to  carve,  then  when  either  ' '  dry  cracks ' ' 
or  rough  places  occur  moisten  the  body  with  a 
camel's-hair  brush  which  has  been  dipped  in  water, 
and  with  it  smooth  off  the  rough  place  and  fill  in  the 
fissures. 

The  approximate  form  of  the  desired  finished 
tooth  should  be  made  of  body,  although  in  many  cases 
it  is  better  to  shorten  the  cutting  edge  somewhat  and 
leave  it  rather  thin,  so  that  the  enamel  which  is  to  be 
fired  over  the  body  will  be  distributed  the  same  way 
as  is  the  enamel  in  a  natural  tooth.     (Fig.  23.)     The 

Fig.  23 


shape  given  to  the  lingual  surface  of  the  carved 
tooth  will  depend  upon  the  use  to  which  the  finished 
tooth  is  to  be  subjected.     If  made  to  be  used  for 


Fig.  24 


attachment  to  a  rubber  base,  it  should  be  formed  as 
shown  in  Fig.  24.  If  to  be  used  for  attachment  to  a 
metal  base,  it  should  be  as  shown  in  Fig.  25. 


PRACTICAL    APPLICATION    OF    BLOCK    BODIES  41 


Pins  lengthwise 


Fig.  25 
Pins  crosswise  Pins  crosswise  near  the  neck 


Drying  the 
Body 


AVhen  the  desired  shape  and  form  have  been 
given  the  tooth,  it  should  be  carefully  dried 
by  holding  it  in  front  of  the  furnace  or  by  passing 
it  gently  through  the  flame  of  a  Bunsen  burner,  and 
when  dry  enough  to  permit  of  handling  it  can  be 
placed  in  a  suitable  platinum  or  fire-clay  support 
(Fig.  26)  which  has  been  previously  covered  with 


Fig.  26 


The  Use 
of  Silex 


coarse  silex.  The  object  in  using  silex  in 
the  firing  pan  or  slide  is  threefold :  it  over- 
comes all  tendency  of  the  porcelain  to  adliere  to  the 
pan,  it  makes  a  porous  bed  of  hot  particles  through 
which  the  heat  can  permeate  to  thoroughly  glaze  the 
under  surface  of  the  porcelain,  and  it  also  permits 
of  gradual  cooling  after  the  firing  of  the  porcelain 
is  complete. 


42 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


Fig.  27 


The  platinum  pins  can  be  placed  in  the  tooth  at 
this  stage  of  the  making,  if  it  is  so  desired,  or  they 
may  be  put  in  place  after  the  first 
firing  when  the  tooth  is  in  the  hard- 
biscuited  condition.  If  placed  in 
position  before  any  firing  has  taken 
place,  precaution  must  be  taken  to 
moisten  the  end  of  the  drill  before 
using  it  to  make  the  holes  for  the 
reception  of  the  pins.  When  the 
pins  have  been  placed  in  posi- 
tion, the  tooth  is  ready  for  the  firing 
process. 

Firing  the  After  all  moisture  has 
Body  been     driven     from     the 

carved  tooth,  it  is  placed  in  the 
furnace  and  subjected  to  a  tem- 
perature necessary  to  hard-biscuit 
the  same.  It  is  then  removed  from 
the  furnace,  allowed  to  cool,  and 
if  any  grinding  or  alteration  is 
necessary  it  may  be  done  by  the 
use  of  sand-paper  disks  or  abra- 
sive wheels. 

The  desired  shade  of  en- 
Enameling  ,  ,  .      -,    . 

amel   can   be  mixed  m  a 

small  mortar  or  saucer  to  the  con- 
sistence similar  to  thick  cream,  and 
in  this  condition  it  can  be  applied 
to  the  biscuited  body  in  about  the 
same  way  in  which  the  enamel  of  a  natural  tooth 
covers  the  dentin  or  bony  portion  of  the  natural  or- 
gan. 

Grasping  the  pins   of  the  biscuited  tooth  in  a 
pair  of  self -locking  tweezers  (Fig.  27)  held  in  one 


PRACTICAL    APPLICATION    OF    BLOCK    BODIES  -Id 

hand,  the  tooth  should  be  slightly  warmed  by  passing 
it  over  the  blue  flame  of  a  burner.  With  a  camel's- 
hair  pencil  held  in  the  other  hand,  the  enamel  is  taken 
up  and  distributed  upon  the  surface,  care  being  taken 
to  lay  it  on  smoothly  and  see  that  no  air  is  inclosed 
in  the  shape  of  bubbles. 

It  is  sometimes  difficult  for  the  beginner  to  apply 
the  enamel  evenly  and  in  such  a  way  as  to  produce  an 
even  distribution  of  shade.  This  difficulty  may  be 
overcome  to  some  extent  by  enameling'  one-half  of 
the  tooth  at  a  time,  or  by  enameling  the  center  from 
neck  to  cutting  edge,  thus  giving  a  side  view  of  the 
thickness  desired,  which  will  act  as  a  guide  in  dis- 
tributing the  enamel  over  the  entire  labial  face  and 
cutting  edge  of  the  crown.  When  thus  enameled,  the 
surfaces  may  be  smoothed,  stained,  made  uneven  to 
imitate  natural  defects,  or  treated  in  any  way  accord- 
ing to  the  result  desired. 

Staining  the  In  staining  hand-made  teeth  it  is  advisable 
Teeth  to  cut  small  grooves  or  lines  in  the  enamel 

surface,  fill  them  in  with  the  desired  stain  and  paint 
a  film  of  enamel  over  it;  this  will  be  productive  of 
very  natural  looking  results,  and  will  permit  of  slight 
grinding  if  that  should  be  necessary  in  the  finished 
tooth. 

Firing  the  After  the  tooth  has  been  enameled  and 
Enamel  stained  to  the  artist's  satisfaction,  it  should 
be  placed  again  upon  the  silex-covered  slide  or  pan 
and  placed  in  a  position  on  or  near  the  furnace, 
where  it  will  receive  a  gradual  drying  out. 

When  thoroughly  free  from  moisture,  the  slide 
can  be  placed  in  the  furnace  and  the  temperature 
raised  to  the  point  necessary  to  vitrify  or  produce 
the  desired  glaze  of  the  enamel. 


44  GILBERT ""S    NOTES    ON    DENTAL    PORCELAIN 

Cooling  Care  must  be  taken  to  prevent  sudden  cool- 

Porcelain  ing  of  the  fired  tooth,  and  to  this  end  it  is 
advisable  to  allow  the  piece  to  remain  in  the  furnace 
until  cool  enough  to  permit  of  removal  with  the 
fingers ;  or  if  the  furnace  is  needed,  and  time  is  too 
precious  to  wait  for  the  cooling,  the  piece  should  be 
removed  while  red  hot  and  quickly  placed  in  an  an- 
nealing oven  made  of  fire  clay,  the  opening  of  which 
can  be  closed  up. 

The  foregoing  brief  description  will  serve  very 
well  as  instruction  for  working,  carving,  and  firing 
a  single  tooth  to  fill  an  edentulous  gap.  The  general 
character  of  a  single  tooth  can  in  most  cases  be  easily 
determined  by  copying  the  corresponding  tooth  on 
the  opposite  side,  but  the  task  is  much  more  difficult 
where  blocks  or  sections  of  sets  are  to  be  made  or 
even  where  odd  teeth  are  desired  for  an  entire  den- 
Artistic  ture.  In  the  latter  cases  it  is  essential  that 
Study  the   worker  be   an   observant   student   of 

the  human  face;  he  must  have  an  appreciative  eye 
and  an  understanding  of  the  great  law  of  corre- 
spondence which  determines  the  size,  color,  and  form 
of  the  teeth  needed  to  harmonize  with  the  age,  tem- 
perament, complexion,  physical  and  ofttimes  the 
moral  attributes  of  the  wearer;  and,  in  addition  to 
possessing  the  power  to  observe  and  appreciate  these 
things,  he  must  be  capable  of  making  his  hands  do 
that  which  his  mind  directs.  For  the  carving  of 
blocks,  therefore,  no  directions  can  be  given  beyond 
those  already  furnished  for  the  making  of  a  single 
tooth.  This  kind  of  porcelain  work  can  only  be  suc- 
cessfully accomplished  by  dentists  who  are  artists  in 
the  highest  sense  of  the  term,  and  therefore  no  in- 
structions can  be  laid  down  on  paper  for  this  class  of 
workmen. 


PRACTICAL    APPLICATION    OF    BLOCK    BODIES  45 

Possibilities  Before  closing  the  chapter  on  block  bodies 
Afforded  by  g^^j  their  practical  application,  mention 
facturers  should  be  made  of  the  possibilities  rendered 
practical  by  the  employment  of  factory-made  teeth, 
the  abrasive  wheel,  and  mineral  stains.  If  the  time 
formerly  devoted  to  the  making  of  hand-carved  teeth 
should  be  utilized  by  the  modern  dentist  in  the  study 
of  the  manufacturers'  stock  of  teeth  and  to  the  altera- 
tion of  these  teeth  to  suit  individual  requirements, 
there  certainly  would  be  a  marked  improvement  in 
prosthetic  dentistry  as  practiced  today. 

In  the  stock  of  the  best  manufacturers  will  be 
found  teeth  not  alone  suited  to  the  general  needs  of 
the  practitioner,  but  there  will  be  found  forms  of 
teeth,  both  plain  and  sectional,  for  metal  or  for 
rubber  work,  especially  designed  to  meet  special  re- 
quirements. By  making  use  of  the  great  variety  thus 
afforded,  the  modern  porcelain  worker  is  equipped 
with  a  base  upon  which  it  is  a  comparatively  easy 
matter  to  work  out  the  esthetic  features  of  a  den- 
ture. In  the  chapter  on  ''Staining  the  Teeth,"  the 
modification  of  manufactured  teeth  and  the  aging  and 
staining  of  the  same  will  be  further  considered. 


CHAPTER    V 


PORCELAIN  CROWNS 

Some  of  the  statements  which  have  been  made 
in  a  previous  chapter  relative  to  hand-carved  teeth 
are  applicable  to  hand-made  artificial  crowns,  al- 
though the  employment  of  the  manufacturers'  ready- 
made  facings  in  the  construction  of  these  crowns  as- 
sists greatly  in  making  this  class  of  porcelain  work 
more  desirable.  As  in  the  case  of  artificial  teeth 
which  are  to  be  attached  to  a  base,  so,  in  the  case  of 
artificial  crowns  suitable  for  attachment  to  the  root, 
manufacturers  now  provide  in  their  regular  stock 
artificial  tooth  crowns  of  many  forms  and  shades, 
suitable  for  all  ordinary  and  a  few  special  require- 
ments of  practice.  For  ordinary  cases  the  average 
dentist  will  find  it  impossible  to  make  by  hand  artifi- 
cial crowns  which  will  compare  favorably  in  point  of 
strength,  adaptability,  and  esthetic  qualities  with 
ready-made  crowns  of  the  Logan  and  Davis  patterns ; 
and  in  some  cases,  where  neither  of  the  above  patterns 
is  applicable  as  supplied,  it  is  far  better  to  use  one 
or  the  other  as  a  base  upon  which  to  build  than  to 
make  an  entire  crown  by  the  hand-carved  method. 
There  are  occasional  cases  presented  which  require 
crowns  totally  different  from  either  the  crowns  or 
facings  supplied  by  the  manufacturer,  and  in  such 
instances  one  or  more  methods  can  be  pursued  in 
manipulating  porcelain  to  meet  the  requirements.  If 
proper  firing  facilities  exist,  block  bodies  may  he 

46 


PORCELAIN      CROWNS 


47 


used  after  the  manner  described  in  the  chapter  de- 
voted to  their  use,  building  the  body  upon  the  dowel 
pin  and  enameling  the  same  in  the  manner  described 
for  enameling  single  teeth.  Another  method  which 
The  Turner  offers  excellent  opportunities  for  the  pro- 
System  for  (Auction  of  entire  porcelain  crowns  will  be 
Making  ^ 

Crowns         found  available  m  the  use  of  ' '  The  Turner 

Porcelain  Crown  and  Bridge  System. ' '  This  method 
comprises  the  use  of  a  set  of  tooth  forms,  molding 

Fig.  28 


rings,  fusible  metal,  and  instruments  for  use  in  con- 
nection with  these  articles.     (Fig.  28.) 

Briefly  described,  this  system  provides  for  the 
making  of  a  porcelain  tooth  in  a  fusible  metal  mold. 


48         gilbert's  notes  on  dental  porcelain 

this  mold  to  be  melted  away  after  the  porcelain  has 
been  poured  or  packed  into  it,  thus  leaving  a  porce- 
lain tooth  in  the  soft  biscuit  or  molded  condition, 
which  can  be  altered  to  meet  desired  requirements. 
Practical  Practical  application  of  this  system  for  the 
Application  construction  of  an  artificial  crown  will  be 
described  as  follows:  The  root  of  the  tooth  to  be 
crowned  should  be  prepared  according  to  the  opera- 
tor's method  of  preparing  roots  for  the  reception  of 
dowel  crowns ;  the  post  and  band  adjusted  to  the  root, 
allowing  the  post  to  extend  below  the  roots  for  about 
one-third  the  length  of  the  tooth  required.  With  the 
post  and  band  in  position  upon  the  root,  take  an 
impression  and  bite  in  the  usual  manner,  from  which 
make  plaster  models.  The  metal  tooth  crowns  de- 
vised for  the  pursuance  of  this  method  have  been 
made  large  enough  to  provide  for  the  shrinkage  of  the 
porcelain;  therefore  select  a  form  which  is  about  one- 
sixth  larger  than  the  desired  porcelain  tooth  and, 
placing  it  (occluding  surface  up)  upon  either  moldine 
or  plastique,  inclose  it  with  the  molding  ring  (small 
diameter  up). 

Owing  to  the  contour  of  the  metal  crowns,  it  is 
necessary  to  make  some  provision  for  releasing  them 
from  the  fusible  metal  after  it  has  been  cast  to  form 
the  mold.  For  this  purpose  it  is  advisable  to  place 
small  nickel-plated  strips  inside  of  the  molding  ring 
in  a  position  which  will  allow  the  metal  mold  to  be 
split  in  a  manner  that  will  release  the  pattern  die. 
Generally  speaking,  these  little  separating  plates 
should  be  at  the  mesial  and  distal  walls  of  the  crown, 
as  shown  in  Fig.  29. 

When  the  pattern  tooth  has  been  placed  in  posi- 
tion upon  the  moldine,  the  separating  plates  adjusted, 
and  the  molding  ring  placed  around  them,  fusible 


POECELAIN      CROWNS 


49 


metal  should  be  melted  and  poured  into  the  ring, 
covering  the  tooth  form  by  an  eighth  of  an  inch  or  so 
of  metal.  "When  the  metal  sets,  but  before  it  is  cool, 
it  should  be  removed  from  the  molding  ring,  the  little 


Fig.  29 


Fig.  30 


separating  strips  knocked  away,  and,  with  the  aid  of 
a  knifeblade  and  mallet,  or,  better  still,  with  the 
Turner  dividers  (Fig.  30),  separate  the  mold,  releas- 
ing the  metal  crown,  and  then,  by  placing  the  parts  of 

4 


50         gilbert's  notes  on  dental  porcelain 

the  fusible  metal  mold  together  again  and  placing 
them  back  in  the  casting  ring,  the  mold  is  ready  to 
receive  the  porcelain. 

In  the  construction  of  porcelain  crowns  made  by 
using  a  mold  such  as  described  there  are  opportuni- 
ties for  displaying  little  or  much  artistic  skill.  The 
crown  can  be  made  of  one  shade  of  porcelain  only, 
or  it  can  be  made  by  blending  two  or  more  shades  to 
reproduce  natural  shades  as  they  exist  at  the  neck 
and  cutting  edge  of  natural  teeth. 
Solid  Shade  If  a  crown  of  one  shade  only  is  to  be  made 
Crowns  in  the  mold,  the  desired  shade  of  porcelain 
should  be  mixed  with  water  to  a  consistence  which 
will  just  permit  of  its  being  dropped  into  the  mold 
from  the  edge  of  a  mixing  spatula.  By  dropping  the 
thick  mix  into  the  mold,  allowing  it  to  strike  the  sides 
and  find  its  way  to  the  bottom,  by  jarring  the  mold, 
there  is  little  danger  of  inclosing  air,  and  thereby 
forming  a  blister  in  the  finished  crown.  As  the  porce- 
lain settles  in  the  mold  the  water  will  remain  on  the 
surface — this  should  be  absorbed  by  bibulous  paper 
or  some  absorbent  cloth;  more  porcelain  is  then 
added,  the  mold  again  jarred  until  the  water  appears, 
when  it  is  again  absorbed  by  pressing  the  absorbent 
down  upon  it,  and  so  on  until  the  mold  is  full,  thus 
making  a  hard,  compact  crown,  which  will  permit  of 
easy  carving,  and  which  when  fired  will  be  hard  and 
dense. 

When  the  crown  has  been  molded,  the  mold  con- 
taining the  porcelain  should  be  removed  from  the 
molding  ring,  placed  in  a  melting  ladle,  and  the  fusi- 
ble metal  melted  away,  allowing  the  porcelain  crown 
free  to  be  handled.  All  particles  of  adhering  metal 
should  be  brushed  away  to  avoid  contamination  with 
the  porcelain,  and  the  crown  is  ready  to  be  carved; 


PORCELAIN      CROWNS  51 

now  the  hole  should  be  drilled  for  the  reception  of 
the  post,  and  any  change  in  form  which  the  model 
indicates  should  be  made,  after  which  it  is  ready  to 
be  fired. 

Shading  If  ^  crown  is  to  be  made  in  which  two  or. 
the  Crown  more  shades  of  porcelain  are  to  be  blended, 
the  mode  of  procedure  is  the  same  as  that  described 
for  a  solid  shade  crown,  except  that  the  desired  shades 
of  porcelain  must  be  placed  in  the  mold  in  such  a  way 
as  to  insure  the  desired  color  effect  in  the  finished 
crown.  To  make  a  crown  in  which  the  cutting  edge 
is  a  yellowish  white,  the  neck  a  decided  yellow,  and 
the  shade  of  the  labial  face  a  gradual  blending  of  the 
shades  in  the  cutting  edge  and  neck,  make  the  fusible 
metal  mold  as  previously  described,  following  the 
detail  of  the  work  up  to  the  point  where  the  porcelain 
is  to  be  placed  in  the  mold.  Two  shades  of  porcelain 
are  to  be  used  in  the  production  of  a  shaded  crown, 
having  the  general  shade  effect  mentioned;  therefore 
select  by  the  shade  guide  the  two  colors — one  which 
approaches  the  shade  desired  for  the  neck  and  an- 
other which  approaches  the  shade  desired  for  the 
cutting  edge.  Mix  each  of  these  porcelains  sepa- 
rately either  on  separate  mixing  slabs  or  far  apart 
on  the  same  mixing  slab. 

The  porcelain  which  is  used  to  produce  the  cutting 
edge  and  assist  in  producing  the  desired  blend  in  the 
labial  face  should  be  placed  in  the  mold  first,  using 
enough  to  fill  the  mold  about  one-third.  Partially 
dry  the  porcelain  with  absorbent  cloth,  and  with  a 
suitable  tool  distribute  it  in  the  mold  by  removing  a 
part  from  the  bottom  of  the  mold  and  packing  it 
against  the  side  which  is  to  form  the  labial  face  of 
.the  tooth  (Fig.  31);  then  drop  the  other  thickly- 
mixed  porcelain  into  the  mold,  absorb  the  water  by 


52         gilbert's  notes  02^  dental  porcelain 

pressing  with  an  absorbent  cloth,  and  release  the 
tooth  by  melting  away  the  fusible  metal  as  before 
described. 

The  distribution  of  the  shades  of  porcelain,  as 
shown  in  the  illustration,  permits  the  darker  or 
underlying  shade  to  show  entirely  at  the  neck,  and, 
by  reason  of  its  having  to  show  through  an  increased 

Fig.  31 


thickness  of  the  lighter  shade  of  porcelain  as  it  ap- 
proaches the  cutting  edge,  the  gradual  blending  of  the 
two  colors  is  effected. 

A  crown  made  from  a  block  body  or  a  good  high- 
fusing  porcelain  will  be  found  hard  enough  to  permit 
of  all  necessary  carving.  A  certain  amount  of  shap- 
ing is  always  necessary  in  order  to  obtain  proper 
relation  of  the  crown  to  the  cap  and  to  occluding 
teeth ;  this  should  be  done  approximately  before  sub- 
jecting the  crown  to  even  a  biscuit  fire. 


FACING  CROWNS 

The  Use  The  various  porcelain  compounds  now 
of  Facings  available  can  be  utilized  in  connection  with 
the  ready-made  facings,  and  the  resulting  crown  will 
generally  be  far  superior  to  crowns  made  by  the 
methods  before  described.    The  facings  sold  by  the 


PORCELAIN      CEOWXS  53 

manufacturers  are  made  from  compounds  having  an 
extremely  high-fusing  point;  by  a  molding  process 
whereby  the  porcelain  is  thoroughly  condensed.  This 
insures  good  texture  and  great  strength,  and  they 
are  supplied  in  a  great  variety  of  form  and  shade. 
In  making  application  of  porcelain  in  connection  with 
manufactured  facings,  it  is  important  to  reinforce 
all  connected  parts  with  a  metal  framework. 
Metal  In  the  construction  of  the  ordinary  cap  and 

Framework  collar  crown,  the  root  should  be  banded 
with  a  narrow  piece  of  platinum  plate  of  No.  28  or 
No.  29  gage,  using  platinum  solder  ( Au.,  75  per  cent. ; 
Pt.,  25  per  cent.)  to  make  the  joint.  To  the  band  a 
piece  of  jolatinum  No.  29  gage,  or  iridio-platinum  of 
No.  30  gage,  should  be  soldered,  forming  the  floor  of 
the  cap.  The  question  of  form  to  be  given  the  anchor- 
post  depends  upon  the  shape  and  size  of  the  canal 
and  upon  the  judgTaent  of  the  worker,  but  whatever 
the  shape  of  the  post,  it  should  be  sufficiently  long 
to  permit  of  firm  anchorage  in  the  natural  root 
and  to  extend  beyond  the  floor  of  the  cap  far 
enough  to  engage  the  pins  of  the  porcelain  facing. 
(Fig.  32.) 

Platinum  solder  should  be  used  in  making  all 
connections,  although  pure  gold  can  be  used  if  care 
be  taken  to  have  no  excess.  When  pure  gold  is  used 
in  excess  there  is  some  danger  of  it  volatilizing  and 
producing  porosity  during  the  subsequent  firing  of 
the  porcelain;  this  is  especially  true  when  block 
bodies  are  employed. 

The  metal  framework  for  bicuspids  and  molars 
calls  for  the  same  general  detail,  with  the  provision  of 
an  additional  metal  post  for  strengthening  and  sup- 
porting the  lingual  cusjos.  Judgment  must  be  exer- 
cised in  determining  the  size  of  this  post,  for  the 


54 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


reason  that  too  much  metal  tends  to  weaken  the 
porcelain,  and  for  this  reason  a  post  just  large 
enough  for  the  requirement  is  indicated.  A  platinum 
pin  taken  from  an  ordinary  vulcanite  tooth,  and  cut 
in  half,  is  just  right  for  the  purpose.     (Fig.  33.) 


Fig.  32 


Fig.  33 


Applying  the  After  the  metal  work  has  been  completed, 
Porcelain  pickled,  tried  in  the  mouth,  and  found  satis- 
factory, the  piece  is  ready  to  receive  the  porcelain. 

Cleanliness  is  essential  in  mixing  the  porcelain, 
which  should  be  placed  on  a  clean  glass  slab  and 
mixed  with  clean  water  to  the  consistence  of  dough. 
Holding  the  work  in  a  pin-vise,  apply  the  porcelain 
and  conform  it  to  the  minutest  crevices  by  tapping 
the  handle  of  the  vise  with  the  mixing  and  carving 
tool. 

The  tapping  will  bring  moisture  to  the  surface, 
where  it  should  be  absorbed  with  blotting-paper  or 
other  absorbent  material.  Gradually  add  the  porce- 
lain until  it  assumes  the  general  form  and  propor- 
tion desired  in  the  finished  crown.  At  this  stage  it 
is  ready  to  receive  the  first  firing.  Saddle-back  teeth, 
countersunk  pin  teeth,  and  Logan  crowns  can  be  used 


PORCELAIN     CEOWNS 


55 


in  the  same  manner  as  facings,  porcelain  being  filled 
in  between  the  cap  and  tooth.    (Figs.  34,  35,  and  36.) 


Fig.  34 


Fig.  35 


Fig.  36 


Biscuit  Fire 


Firing  the  Crowns  which  have  been  made  as  above 
Crowns  described  will  have  to  be  subjected  to  more 
than  one  firing,  owing  to  the  fact  that  the  first  fire 
will  cause  shrinkage,  which,  in  turn,  causes  fissures 
in  the  porcelain. 

In  the  first  firing  of  a  crown  it  is  only 
necessary  to  carry  the  temperature  high 
enough  to  effect  shrinkage,  thus  showing  the  worker 
where  the  fiUing-in  must  be  done.  This  is  called  the 
'^Discuit  fire,"  and  is  recognized  as  that  stage  of  the 
firing  process  when  the  porcelain  becomes  hard  but 
not  glossy,  when  shrinkage  has  taken  place,  and  the 
mass  seems  to  be  covered  with  minute,  shining  par- 
ticles. If  allowed  to  remain  in  the  furnace  until  the 
porcelain  is  glazed,  the  chances  are  that  in  the  final 
firing  the  porcelain  will  "sputter,"  and  thus  produce 
a  porous,  weak,  and  dirty-looking  crown.  A  crown 
which  has  been  made  of  good  porcelain  and  properly 
biscuited  will  have  lost  about  one-sixth  of  its  bulk 
in  the  biscuit  fire.    After  the  crown  has  received  its 


56 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


biscuit  ''fire,"  it  can  be  tried  upon  the  articu- 
lating model  and  the  porcelain  ground  off  or  added 
where  necessary  to  proper  occlusion  and  approximal 
contact.  For  the  second,  which  is  generally  but  not 
always  the  final,  firing,  the  desired  shade  of  porce- 
lain is  mixed  and  carefully  added  to  the  crown  until 
it  is  slightly  larger  than  is  required.     Experience 


Fig.  39 


Fig.  40 


only  will  determine  just  how  much  extra  porcelain 
will  be  needed ;  it  all  depends  upon  the  care  taken  to 
absorb  the  moisture  during  application  of  the  porce- 
lain and  upon  the  grade  of  porcelain  used.  If  the 
porcelain  is  "wet"  when  applied,  the  fire  will  cause 
more  shrinkage  than  it  would  if  the  porcelain  had 
been  applied  dry,  that  is,  with  the  minimum  of  mois- 


PORCELAIN     CROWNS  57 

ture.  In  the  final  firing,  the  heat  should  be  applied 
gradually  and  the  crown  allowed  to  remain  in  the 
furnace  until  the  porcelain  assumes  a  smooth,  glossy 
surface  corresponding  to  that  of  natural  enamel. 

Fig.  37  shows  three  finished  molar  crowns  made  of 
solid  porcelain,  no  facings  being  used. 

Figs.  38,  39,  and  40  show  finished  anterior  crowns 
with  facings. 


CROWNS  FOR  EXPOSED  ROOTS 

There  is  sometimes  presented  a  case  for  crowning 
in  which  recession  of  the  gums  has  exposed  a  con- 
siderable portion  of  the  root,  thus  throwing  the  gin- 
gival margin  out  of  alignment  with  that  of  the  ad- 
joining teeth.  In  such  cases  a  porcelain  crown  can  be 
adjusted  and  will  often  be  productive  of  better  results 
than  can  be  achieved  by  any  other  method  of  restora- 
tion. A  cap  and  collar  crown  is  indicated,  and  the 
method  of  constructing  it  is  practically  the  same  as 
that  described  for  the  construction  of  a  porcelain 
crown  with  porcelain  facing. 

A  band  of  platinum,  No.  34  gage,  is  made  to 
accurately  fit  the  root  and  follow  the  line  of  the  gum, 
and  to  this  band  is  soldered  the  floor,  making  a  cap  as 
before  described.  When  making  the  band  for  such 
cases  it  is  advisable  to  first  make  a  pattern  of  tea- 
lead  or  of  tin-foil.  This  is  readily  done  by  cutting 
the  pattern  metal  approximately  to  shape  and  then 
laying  it  upon  the  root  and  swaging  it  to  place  with 
an  eraser  on  the  end  of  a  lead  pencil,  pieces  of  spunk, 
or  any  other  easy  method  which  may  suggest  itself. 
If  the  platiiuim  is  cut  to  correspond  to  this  soft  metal 
pattern,  it  will  be  easily  adapted  to  the  root  and 


58         gilbert's  notes  on  dental  porcelain 

outline  of  the  gum.  When  an  accurate  fit  is  obtained, 
the  band  soldered  and  attached  to  the  floor,  the  pin 
should  be  fitted  to  place,  the  porcelain  facing  sol- 
dered to  the  post,  and  the  whole  placed  in  the  pickling 
bath  and  made  ready  to  receive  the  porcelain.  After 
the  lingual  surface  of  the  crown  has  received  its  first 
application  of  porcelain,  and  before  any  firing  has 
taken  place,  that  portion  of  the  band  which  is  to 
replace  the  lost  gum  line  should  be  scratched  or 
roughened  with  an  excavator  and  then  covered  with 
a  thin  layer  of  yellow  porcelain,  after  which  the 
crown  is  placed  in  the  furnace  and  the  porcelain 
carried  to  a  "biscuit  fire."  The  object  of  placing  a 
layer  of  yellow  porcelain  on  that  portion  of  the  band 
which  is  to  receive  gum  enamel  is  to  give  added 
strength  to  the  crown  at  this  point  and  also  to  tone 
down  the  color  of  the  gum.  A  yellow  shade  of  porce- 
lain is  recommended  because  that  is  the  color  which 
is  generally  indicated  for  use  in  connection  with  gum 
enamel,  but,  of  course,  the  judgment  of  the  worker 
must  at  all  times  indicate  whether  this  underlying 
color  should  be  yellow,  brown,  white,  or  some  other 
shade.  If  a  bright,  lifelike  gum  is  indicated,  yel- 
low as  an  underlying  color  will  generally  give  the  de- 
sired result ;  while  if  the  desired  shade  of  gum  is  of  a 
muddy,  dark  color,  brown  will  be  found  to  give  the 
best  results.  "White  as  an  underlying  color  will  pro- 
duce a  pale  gum.  After  the  biscuiting  has  been  done, 
the  shrinkage  cracks  should  be  filled  in,  the  proper 
amount  of  porcelain  added  to  the  lingual  surface,  the 
gum  enamel  put  in  its  proper  place,  and  the  crown 
again  placed  in  the  furnace,  this  time  carrying  the 
temperature  up  to  the  glazing  point  of  the  porce- 
lain. Especial  care  must  be  exercised  in  cooling  a 
crown  of  this  description,  for  if  subjected  to  draughts 


PORCELAIN     CROWNS 


59 


of  air  or  allowed  to  cool  too  quickly,  minute,  hair- 
like cracks- will  appear  in  the  gum  enamel. 

Fig.  41  shows  a  crown  such  as  has  been  described; 


Fig.  41 


a  representing  the  metal  framework  before  porce- 
lain has  been  applied,  and  h  representing  the  fin- 
ished crown. 


PORCELAIN  CROWNS  WITH  GOLD  BANDS 


Some  practitioners  have  objections  to  the  appli- 
cation of  porcelain  crowns  owing  to  the  fact  that 
platinum  must  be  used  for  the  construction  of  all 
metal  parts.  The  chief  objection  to  platinum  in  this 
connection  lies  in  the  fact  that  it  is  dark  in  color,  and 
where  bands  are  exposed  to  view  a  dark  line  is 
apparent,  which  suggests  decay.  It  has  been  sug- 
gested that  in  such  cases  as  mentioned  the  finished 
porcelain  crown  can  be  subjected  to  a  plating  solution, 
which  will  deposit  upon  its  metal  parts  a  substantial 
layer  of  gold,  thus  overcoming  the  color  objection. 

Another  method  of  making  crowns  whereby  the  de- 
sirable features  of  an  all-porcelain  crown  can  be  ob- 


60 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


tained  without  the  objectionable  features  of  platinum 
is  by  the  use  of  crowns  similar  in  form  to  the  English 
tube  teeth.  These  crowns  may  be  made  after  the 
manner  described  for  application  of  the  Turner  sys- 
tem, a  tube  of  platinum  being  inserted  in  the  center  of 
the  little  metal  mold  and  the  porcelain  packed  around 
it,  or  a  hole  can  be  drilled  through  the  biscuited  crown 
before  firing  it  to  a  glaze.  In  the  latter  case,  of 
course,  there  will  be  no  platinum  tube,  and  this  is  not 
necessary,  because  the  tooth  can  be  fixed  to  the 
post  with  sulphur  or  cement  instead  of  soldering, 
as  is  sometimes  done  with  the  teeth  provided  with 

Fig.  42 


a  tube  of  platinum.  To  make  practical  applica- 
tion of  a  crown  made  as  above  described,  the  root 
should  be  prepared  in  the  same  way  as  for  the  recep- 
tion of  the  ordinary  Richmond  crown.  A  gold  cap 
is  then  fitted  to  the  root  and  pin  adjusted  to  the  canal, 
allowing  it  to  extend  the  entire  length  of  the  desired 
tooth  below  the  band.  The  post  in  this  case  should 
be  round,  with  a  flat  filed  on  the  tooth  end  to  prevent 
turning.  This  post  should  not  be  soldered  to  the 
cap  until  the  fitting  of  the  porcelain  tooth  to  the  cap 
has  been  made,  but  it  should  be  fixed  in  position  with 
wax.  When  prepared  in  this  way,  an  impression  of 
the  parts  should  be  taken  with  the  cap  and  post  in 
position.     (Fig.  43.) 


PORCELAIN      CROWNS  61 

Before  pouring  the  plaster  into  this  impression, 
the  post  and  cap  should  each  be  coated  with  a  film  of 
soft  wax,  so  that  when  the  model  has  been  made  the 
cap  and  the  post  can  be  removed  from  and  placed  back 
into  position  as  often  as  may  be  necessary  during  the 
The  Use  fitting  of  the  porcelain.  Eeady-made  crowns 
ofPinless  like  the  Davis,  English  tube  teeth,  Bonwill, 
Crowns  ^^^  Foster  crowns  can  be  mounted  upon 
roots  in  this  way  by  grinding  them  to  fit  cap  and 
occlusion ;  but,  with  the  exception  of  the  Davis,  these 
crowns  are  not  carried  in  the  regular  stock  of  the 
manufacturers,  and  their  employment  is  therefore 
almost  prohibited.  Wlien  making  a  crown  from 
either  block  body  or  a  high-fusing  porcelain,  to  be 
mounted  upon  a  gold  cap,  it  is  important  to  make 
the  molded  or  carved  crown  considerably  longer  than 
the  desired  finished  crown.  This  must  be  done  in 
order  to  provide  the  necessary  amount  of  material 
at  both  the  root  and  occlusal  end,  to  facilitate  fitting. 

Having  prepared  the  model  so  that  the  cap  and 
post  can  be  easily  removed  and  replaced,  remove 
the  post,  allowing  the  cap  to  remain  in  its  posi- 
tion upon  the  model;  then  take  a  long,  thin  instru- 
ment (thinner  than  the  crown-post),  place  the  point 
in  the  hole  where  the  post  was,  and  drill  a  hole 
through  the  plaster  cast,  taking  care  to  make  this 
hole  a  straight  continuation  of  the  original  post  hole. 
The  purpose  of  this -hole  in  the  model  will  be  ex- 
plained later.  Now,  with  the  post  out  of  the  way,  the 
molded  or  carved  crown  may  be  fitted  to  the  model 
for  approximal  contact,  occlusion,  and  position  on  the 
cap.  When  such  fitting  and  adjustment  has  been 
made,  the  crown  should  be  held  in  position  and  the 
long,  pointed  drill  placed  in  the  hole  at  the  back  of  the 
model  and  gently  advanced,   drilling  through  the 


62         gilbert's  xotes  ox  dental  porcelain 

crown,  thus  determining  the  correct  position  of  the 
hole.     (Fig.  43.) 

Fig.  43 


The  hole  in  the  crown  should  then  be  made  just 
large  enough  to  accommodate  the  round  post,  and  this 
should  be  done  before  the  crown  receives  its  biscuit 
fire.  In  order  to  keep  this  hole  in  its  original  position 
and  prevent  any  tendency  to  close  up  during  the 
subsequent  firings  of  the  crown,  it  should  be  filled 
Another  Use  with  fine  silex,  care  being  taken  not  to  pack 
for  Silex  the  silex,  but  to  place  it  in  the  hole  without 
using  pressure.  Silex  is  infusible  at  temperatures 
required  to  glaze  dental  porcelains.  Itwill  not  shrink, 
so  it  can  be  readily  removed  when  the  crown  is  finished 
and  ready  for  mounting.  The  method  for  firing  the 
pinless  crown  is  the  same  as  described  for  either  the 
carved  or  porcelain  facing  crown.  The  post  should 
now  be  joermanently  soldered  to  the  cap,  and  the  final 
fitting  of  the  porcelain  to  the  gold  cap  can  be  accom- 
plished by  "inking  down"  the  joint.  This  is  done  by 
mixing  Prussian  blue  with  oil,  applying  it  lightly  to 
the  surface  of  the  porcelain  to  be  fitted,  grinding 
where  indicated,  and  trying  it  on  the  cap  from  time 
to  time  until  a  good  joint  has  been  secured.    When 


PORCELAIN     CROW  Is  S 


63 


making  this  joint  between  cap  and  porcelain,  care 
must  be  exercised  not  to  shorten  the  bite,  and  thus 
destroy  the  articulation. 


MOUNTING 

Attaching  When  the  crown  has  been  cleaned  by  remov- 
Pin  to  ing  all  traces   of  oil,   etc.,   and  the  post 

Crown  roughened  to  facilitate  attachment  of  the 

luting  material,  the  crown  can  be  mounted,  using 
either  sulphur  or  cement  for  the  purpose.  If  sulphur 
is  used,  it  should  be  melted  in  a  porcelain  cup,  and, 
when  in  a  fluid  condition,  dipped  from  the  cup  with 

Fig.  44 


a  sharp-pointed  instrument  and  dropped  into  the  hole 
of  the  crown,  which  should  be  gently  heated.  Capil- 
lary attraction  will  cause  the  sulphur  to  run  into  all 
interstices,  and  any  excess  which  may  run  over  can 
be  cut  away  with  a  sharp-pointed  instrument  when 
the  sulphur  becomes  hard. 

Fig.  44  illustrates  a  second  bicuspid  made  and 
adapted  as  above  described. 


CHAPTER    VI 


PORCELAIN   FILLINGS 

The  modern  porcelain  filling  has  attained  its 
present  popularity  through  the  improved  facilities 
which  have  been  made  available  for  the  manipulation 
of  the  material. 

Porcelain  Notwithstanding  the  fact  that  the  profes- 
Fillings  sion  as  a  whole  made  little  use  of  porcelain 
Not  New  as  a  filling  material  until  the  few  years  just 
past,  the  underlying  principles  for  its  employment 
were  made  known  as  far  back  as  1886. 

The  principles  governing  the  preparation  of  the 
cavity — the  making  of  a  metal  matrix,  the  firing  of 
the  porcelain,  and  the  setting  of  the  finished  inlay — 
were  fully  described  by  Dr.  Chas.  H.  Land,  of 
Detroit,  Mich.,  in  articles  published  in  the  Independ- 
ent Practitioner  of  August  1886,  and  February  1887. 
With  the  exception  of  a  few  enthusiastic  dentists  who 
appreciated  the  inlierent  merits  of  porcelain  and  who 
have  been  willing  to  accept  all  of  the  difficulties  at- 
tending its  application  to  dentistry,  this  material 
received  little  attention  until,  as  before  intimated, 
modern  conveniences  made  its  employment  practical. 

Those  men  who  made  practical  use  of  porcelain 
between  the  time  of  its  introduction  and  the  begin- 
ning of  the  present  porcelain  era  have  been  persistent 
in  their  statements  that  ''porcelain  restorations  are 
practical  and  have  stood  the  test  of  time."  These 
statements  have  been  made  in  the  face  of  adverse 

64 


PORCELAIN     FILLINGS 


65 


criticism  and  even  ridicule,  and  it  must  now  be  a 
source  of  much  comfort  for  the  pioneers  to  witness 
the  interest  in  and  hear  the  favorable  claims  which 
are  now  made  for  this  tooth-saving  and  tooth-restor- 
ing agent. 

By  some  practitioners  porcelain  is  regarded  as 
the  ideal  material  for  filling  the  natural  teeth,  thus 
claiming  for  it  all  the  essential  and  desirable  features 
which  that  long-sought-for  material  should  possess. 
Others  think  porcelain  is  indicated  only  in  those  cavi- 
ties which  are  conspicuously  located  and  in  which 
fillings  are  not  subject  to  the  force  of  mastication. 
The  esthetic  results  capable  of  acquirement  by  tbe 
use  of  suitable  porcelain  probably  appeals  to  the 
average  dentist  more  than  any  other  quality.  This 
quality,  while  very  desirable,  is  not  absolutely  essen- 
tial, and  if  porcelain  is  to  be  regarded  as  a  suitable 
material  for  filling  teeth,  it  must  possess  the  essential 
qualities. 

Value  of  Porcelain  workers  of  experience  now  claim 
Porcelain  that  inlays  are  more  durable  than  the  aver- 
age gold  filling;  that  recurrence  of  decay  around  the 
margin  of  an  inlay  is  unknown.  If  this  is  so,  then 
we  must  credit  porcelain  inlays  with  the  quality  of 
durability.  Porcelain  is  compatible  with  natural 
tooth  structure,  its  esthetic  qualities  are  unsurpassed 
by  any  other  material,  and  it  is  now  practical  to 
employ  it.  . 

In  addition  to  possessing  these  essentials,  the 
necessary  formation  of  the  cavity  to  receive  a  porce- 
lain inlay  makes  it  an  available  and  desirable  filling 
material  for  the  teeth  of  nervous  individuals  who 
cannot  tolerate  the  long  sittings  necessary  for  the 
insertion  of  metallic  fillings.  Another  claim  made  for 
inlays  is  to  the  effect  that  recurrence  of  decay,  should 


66 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


it  occur,  is  readily  discovered  under  fillings  which 
owe  their  retention  to  adhesion,  while  decay  under 
fillings  which  owe  their  retention  to  the  shape  of  the 
cavity  is  often  undiscovered  until  pulp  infection  has 


Fig.  45 


taken  place.  It  will  be  understood  from  the  foregoing 
claims  made  for  porcelain  fillings  that  there  is  good 
reason  for  their  existence.  The  proper  manipulation 
of  porcelain  in  the  construction  of  inlays  calls  for  the 
exercise  of  much  judgment  and  skill.    The  knowledge 


POKCELAIN      FILLINGS 


67 


of  the  dentist,  the  judgment  of  the  mechanic,  and  the 
skill  of  the  artist  are  all  required  if  the  full  comple- 
ment of  porcelain's  qualities  is  to  be  made  manifest. 
Experimen-  Experimental  work,  and  plenty  of  it,  should 
tal  Work  be  performed  in  the  laboratory  before  mak- 
ing practical  application  to  natural  teeth.  The  technic 
of  porcelain  work  differs  from  all  other  heretofore 

Fig.  46 


performed  by  the  dentist.  Starting  with  the  prepara- 
tion of  the  cavity  and  following  it  through  the  pro- 
cesses of  matrix  formation,  mixing  and  application  of 
the  porcelain,  the  running  of  the  furnace  and  firing  of 
the  inlay,  its  subsequent  cooling  and  insertion  in  the 
cavity— all  these  steps  necessitate  practice  before  the 
best  results  can  be  obtained. 

For  the  convenience  of  the  novice,  some  of  the 
manufacturers  offer  experimental  outfits,  consisting 
of  molds  for  the  making  of  technic  teeth  (Fig.  45), 
ready-made  technic  teeth,  etc.  The  object  of  these 
experimental  outfits  is  to  provide  a  means  whereby 


68         gilbert's  notes  on  dental  porcelain 

the  student  or  practitioner  may  perfect  himself  in  the 
technic  of  inlay  making.  They  afford  most  of  the 
Technic  essentials  for  practice  in  every  feature  of 
Teeth  inlay  construction,  and  one  or  all  of  these 

outfits  should  be  extensively  used  by  students  who 
wish  to  obtain  perfection  in  every  detail  of  the  work. 
Finished  technic  teeth  in  which  cavities  have  been 
prepared  (Fig.  46)  afford  an  excellent  base  upon 
which  to  practice  the  burnishing  of  the  matrix,  but 
for  all-around  experimental  work  the  biscuited 
technic  teeth  (Fig.  47)  are  better  adapted  to  serve  all 

Fig.  47 


requirements.  These  biscuited  teeth  are  made  from 
The  S.  S.  White  Dental  Manufacturing  Co.'s  High- 
Fusing  Porcelain.  They  have  been  pressed  in  molds, 
thus  rendering  them  firm  and  hard  enough  to  be 
handled  and  carved  at  pleasure.  Cavities  of  any 
description  can  be  prepared  according  to  the  indi- 
vidual practitioner's  idea  of  cavity  formation. 


CAVITY  PREPARATION 

The  student  or  practitioner  who  has  been  accus- 
tomed  to   preparing   cavities    for   other   materials 


PORCELAIN     FILLINGS  69 

must  change  his  methods  and  plans  when  preparing 
those  which  are  to  receive  inlays.  In  the  prepara- 
tion of  such  cavities  the  operator  must  have  in  mind 
the  removal  of  the  matrix,  the  taking  of  an  impres- 
sion, if  the  inlay  is  to  be  made  by  swaging  methods, 
the  strength  of  the  edges  of  the  finished  inlay,  and  the 
strain  which  the  inlay  must  withstand  during  mastica- 
tion. 

Experience  has  taught  us  that  the  thin  porcelain 
veneer  is  limited  in  its  application  to  those  localities 
where  no  strain  can  take  place,  and  that  the  so-called 
saucer-shaped  cavity  is  not  at  all  indicated  for  the 
reception  of  porcelain  except  in  rare  instances.  The 
strength  of  a  porcelain  inlay  depends  largely  upon 
its  bulk  and  upon  the  nature  of  the  force  exerted 
upon  it;  this  is  especially  true  of  the  edge  strength. 
The  advice  given  by  practical  men  regarding  the 
necessity  of  perpendicular  walls  and  flat  bases 
shows  that  this  truth  is  being  generally  recog- 
nized. 

Definite  rules  for  the  formation  of  cavities  for 
inlays  cannot  be  established  to  any  greater  extent 
than  they  can  be  established  for  filling  materials  of 
another  sort,  but  there  are  general  principles  under- 
lying the  essential  features  which  may  be  recom- 
mended. The  typical  cavities  illustrated  by  Dr.  A.  E. 
Peck  will  serve  to  demonstrate  these  principles  per- 
haps better  than  anything  else  known  to  the  writer; 
and  if  the  beginner  will  study  them,  and  will  perfect 
himself  in  the  technic  of  preparing  similar  cavities  in 
"experimental  teeth"  and  of  making  inlays  to  fit 
them,  it  will  prove  of  great  help  to  him  when  the 
time  comes  for  making  his  own  modifications  of  these 
typical  cases  to  fulfill  requirements  demanded  by 
practical  necessities. 


70         gilbert's  notes  on  dental  porcelain 

Typical         Dr.  Peck's  classification  of  cavities  is  as 
Cavities         follows : 

Cavities  involving  one  surface,  labial  cavities. 

Cavities  involving  more  than  one  surface,  mesio- 
labial. 

Cavities  involving  mesio-labial-lingual  surfaces. 

Cavities  involving  mesio-labial-lingual  incisal  sur- 
faces. 

Cavities  involving  labial-lingual-incisal  surfaces. 

Cavities  involving  the  entire  incisal  edge. 

Cavities  involving  the  approximal  and  occlusal 
surfaces  of  the  posterior  teeth. 

Cavities  involving  the  whole  occlusal  surface  of 
the  posterior  teeth. 

For  the  purpose  of  experimenting  it  is  not  neces- 
sary for  the  beginner  to  prepare  cavities  like  all 
which  have  been  described  and  make  inlays  for  them, 
although  if  this  is  done,  the  knowledge  gained  will 
be  worth  the  effort.  The  essential  lesson  to  be 
learned  from  this  experimental  work  is  that  certain 
mechanical  principles  govern  the  preparation  of  a 
cavity  for  the  reception  of  a  porcelain  filling,  and  if 
this  lesson  be  fully  understood  all  cavities  will  in  a 
The  Principle  nianner  be  alike,  embodying  as  they  do  the 
Involved  application  of  a  simple  principle — flat 
bases  and  straight  walls. 

Experimental  cavities  may  be  prepared  in  ex- 
tracted natural  teeth,  but  unless  very  strong  newly 
extracted  teeth  are  used,  such  teeth  will  be  found 
too  weak  and  brittle  to  withstand  the  necessary  cut- 
ting and  subsequent  treatment  required  in  either  bur- 
nishing or  swaging  the  matrix.  If  the  beginner  will 
use  the  technic  teeth  provided  in  the  experimental 
outfit,   he   will   find   them   much   better   suited   for 


PORCELAIN     FILLINGS 


71 


the  purpose,  for  they  can  be  cut  with  disks  and 
ground  with  abrasive  stones  without  danger  of  split- 
ting, and  they  will  stand  the  necessary  burnishing 
and  swaging  without  fracturing  at  the  edges. 

Perhaps  the  best  technic  teeth  available  for  the 
preparation  of  cavities  are  those  made  by  The  S.  S. 
White  Dental  Mfg.  Co.,  and  which  are  supplied  to 
the  profession  in  the  soft-biscuited  condition.  These 
teeth  are  made  in  forms  of  centrals,  laterals,  cuspids, 
and  molars  (see  Fig.  47) .     The  porcelain  from  which 


Fig.  48 


Fig.  49 


Shown  twice  the  actual  size 


they  are  made  can  be  carved  to  any  desired  form,  and 
it  can  be  fired  in  any  of  the  ordinary  electric  furnaces 
which  dentists  are  now  using.  Taking  one  of  these 
biscuited  teeth  for  the  purpose  of  illustration,  the 
technic  of  preparing  several  cavities  involving  differ- 
ent surfaces  of  the  tooth  may  be  described  as  follows : 
Fig.  48  shows  an  enlarged  view  of  a  cavity  on  the 
labial  surface  of  an  incisor  which  has  been  prepared 
for  the  reception  of  a  filling,  illustrating  the  general 


72 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


outlines  and  the  perpendicular  walls.  A  sectional 
view  (Fig.  49)  of  the  same  tooth  shows  the  depth  of 
the  cavity,  the  perpendicular  walls,  flat  base,  and 
slight  curve  at  the  juncture  of  the  walls  and  base. 

Fig.  50  shows  a  cavity  involving  part  of  the  labial 
and  part  of  the  approximal  surface.  It  shows  the  gen- 
eral outline  of  the  cavity,  the  straight  walls,  and  the 
retaining  groove  running  along  the  lingual  wall.  The 
second  view  (Fig.  51)  shows  the  straight  walls  and 


Fig.  50 


Fig.  52 


Fig.  51 


the  depth  of  the  groove.  A  practical  cavity  of  this 
formation  can  be  filled  with  but  little  separation  of 
the  teeth. 

Fig.  52  shows  a  view  of  a  cavity  involving  part  of 
the  labial,  approximal,  and  lingual  surfaces.  This 
cavity  is  of  the  same  general  formation  as  that  shown 
in  Fig.  50.  The  lingual  wall  has  been  cut  away  and 
the  retaining  groove  cut  in  the  body  of  the  tooth,  thus 
making  the  finished  inlay  wedge-shaped,  with  the 
small  end  toward  the  labial  wall. 


PORCELAIN"  FILLINGS 


73 


Fig.  53  shows  a  cavity  involving  the  cutting  edge. 
An  inlay  made  to  fit  this  cavity  will  be  wedge-shaped, 
with  the  small  end  toward  the  labial  wall  and  the 
retentive  ridge  running  along  the  top  and  part  way 
along  the  sides. 

To  prepare  experimental  cavities  such  as  have 
been  described,  a  square-end  fissure  bur  should  be 
used  to  make  the  flat  base,  the  corners  at  juncture 


Fig.  53 


Fig.  54 


Fig.  55 


I 


of  walls  and  base  should  be  slightly  rounded  with  a 
pear-shaped  bur,  and  the  walls  made  perpendicular 
with  the  side  of  a  fissure  bur. 


74 


GILBERT'S    XOTES    ON    DENTAL   PORCELAIN 


When  the  teeth  have  been  fired,  the  walls  and  edges 
can  be  made  smooth  and  sharp  with  either  diamond 
burs  or  very  fine  abrasive  points.    (Figs.  55  and  56.) 


Fig.  5G 


mu  ^ 


E 


Having  prepared  an  experimental  cavity  as  de- 
scribed, 'an  impression  can  be  made  either  by  burnish- 
ing the  metal  matrix  into  the  cavity  by  means  of  the 
proper  shaped  instruments,  or  by  the  swaging  method 
or  by  a  combination  of  both. 

Making  The  essential  point  in  making  matrices  is  to 
the  Matrix  obtain  a  correct  impression  of  the  cavity  in 
either  gold  or  platinum  foil,  according  to  the  kind  of 
porcelain  to  be  employed.  That  method  by  which  the 
worker  can  best  bring  about  this  adaptation  of  the  foil 
to  the  cavity  is  the  method  for  him  to  use.  The  fol- 
lowing method  for  making  a  matrix  of  platinum  foil 
and  completing  an  inlay  of  high-fusing  porcelain  will 
be  found  generally  useful,  using  a  cavity  like  that 
shown  in  Fig.  57  as  the  illustration :  Platinum  foil, 
1/1000  of  an  inch,  is  first  annealed  by  placing  it  in 
the  electric  furnace  when  the  muffle  is  red  hot  and 
allowing  it  to  remain  in  the  muffle  until  the  foil  is  cool 


PORCELAIN  FILLINGS 


75 


enough  to  be  taken  out  with  the  fingers.  This  anneal- 
ing can  be  done  without  the  loss  of  any  time  by  using 
Annealing  the  last  heating  of  the  furnace  for  this  pur- 
Platinum  Foil  pose;  that  is  to  say,  when  the  furnace  is 
being  used  for  the  last  time  on  an}'-  day,  place  a  sheet 
of  foil  in  the  hot  mutfie,  turn  off  the  current,  and 
allow  the  foil  to  remain  until  the  next  day,  at  which 
time  it  will  be  found  free  from  "rattle,"  soft,  and 
pliable.  By  keeping  a  sheet  or  so  of  platinum  on  hand 
it  can  be  kept  ready  annealed  for  use  at  any  time. 


Fig.  57 


Fig.  58 


Cut  the  foil  to  approximate  shape  and  a  size  that 
will  permit  of  easy  adaptation  to  the  cavity,  and 
allow  a  small  margin  to  overlap  the  edges  to  assist 
in  the  removal  of  the  matrix,  and  as  a  guide  for  ob- 
taining proper  contour  when  the  porcelain  is  placed 
in  the  matrix.     (Fig.  58.) 

The  initial  adaptation  of  the  foil  to  the  cavity  can 
be  made  by  grasping  pieces  of  spunk  in  the  beaks 
of  ball-pointed  pliers  (Fig.  59)  and  pressing  them 
upon  the  foil  and  into  the  cavity. 


76         gilbert's  notes  ox  dental  porcelain 


Fig.  59 


•3i: 


PORCELAIN   FILLINGS  77 

This  pressing  of  the  foil  with  spunk  will  cause  the 
matrix  to  fold  upon  itself  in  some  places,  but  these 
folds  can  be  burnished  out  with  steel  instruments, 
(Fig.  60.)  Burnishing  will  cause  the  metal  to  become 
harsh,  and  it  should  therefore  be  annealed  frequently 
during  the  fitting,  each  time  placing  the  matrix  in  the 
hot  muffle  of  the  furnace  rather  than  in  the  flame  of 
a  Bunsen  burner.  When  annealing  the  matrix  in  this 
way,  of  course  it  is  not  necessary  to  allow  the  fur- 
nace to  cool  each  time,  as  was  recommended  pre- 
viously for  the  initial  annealing,  but  simply  place  the 
matrix  in  the  muffle,  allow  it  to  remain  for  a  minute, 
and  remove.  If  the  initial  burnishing  is  started  at  the 
bottom  of  the  cavity  by  giving  a  rotary  movement 
to  the  instrument  and  gradually  burnishing  toward 
the  edges  of  the  cavity,  the  folds  in  the  metal  are 
easier  to  straighten  out  than  if  the  burnishing  is  done 
from  the  edges  toward  the  center  of  the  cavity. 
To  Eliminate  As  an  aid  to  eliminating  folds  as  they  occur 
Folds  at  the  edges,  it  is  well  to  cut  V-shape  pieces 

from  the  overhang;  this  will  avoid  "buckling"  and 
relieve  the  tendency  in  the  metal  to  spring  away  from 
one  wall  while  another  is  being  burnished.  When  the 
matrix  has  been  adapted  to  the  walls  of  the  cavity  by 
the  burnishing,  it  should  again  be  annealed,  placed 
back  in  the  cavity,  and  swaged  by  using  a  stick  of 
Dental  Lac  Dental  Lac.  Dental  Impression  Lac  is  best 
as  a  Swager  softened  by  dry  heat,  and  this  is  done  by 
passing  a  stick  of  it  over  the  flame  of  the  lamp  or 
burner,  taking  care  not  to  reach  the  melting  point. 
Before  pressing  the  Lac  into  the  matrix  the  cavity 
and  the  Lac  should  be  moistened  and  the  Lac  pressed 
into  the  cavity,  thus  making  a  die.  Again  moisten  the 
Lac  die  and  swage  the  matrix  to  the  cavity.  The 
matrix  usually  comes  away  from  the  cavity  with  the 


78         gilbert's  notes  on  dental  porcelain 

Lac,  from  which  it  can  be  easily  removed  with  the 
inlay  pliers.  Should  any  folds  or  thick  places  remain 
along  the  edges  of  the  matrix,  it  can  be  again  bur- 
nished and  swaged,  after  which  it  is  ready  to  receive 
the  porcelain  compound. 

Dr.  C.  C.  Allen  recommends  the  following  method, 
which  greatly  facilitates  the  making  of  a  matrix: 
Gum  After  obtaining  an  approximate  adaptation 

Camphor  of  the  matrix  to  the  cavit}^,  fill  the  matrix 
with  gum  camphor,  pack  it  hard,  thus  actually  swag- 
ing the  matrix  against  the  cavity  walls.  Burnish  the 
edges  of  the  matrix  until  they  are  perfectly  smooth. 
To  remove  the  matrix  without  changing  its  form, 
insert  a  sharp-pointed  instrument  in  the  body  of  the 
camphor  and  lift  the  camphor,  matrix,  and  all  out  of 
the  cavity.  After  investing  the  matrix,  the  camphor 
can  be  burned  out,  leaving  no  residue.  Should  the 
camphor  have  become  contaminated  with  blood,  it 
may  be  removed  by  soaking  for  a  few  minutes  in 
alcohol. 

Taking  Another  method  of  adapting  a  matrix  to 

Impressions  the  cavity,  and  one  which  is  thought  by 
some  to  be  superior  to  the  burnishing  method,  is  by 
taking  an  impression  of  the  cavity,  making  a  model, 
and  swaging  the  matrix  between  die  and  counter- 
die.  The  impression  can  be  taken  in  wax,  modeling 
composition,  or  cement,  according  to  the  subsequent 
method  of  using  such  impressions.  If  wax  is  used 
as  the  impression  material,  it  should  be  softened  by 
passing  over  the  flame  of  a  burner  and  then  dipped 
into  soapstone,  whiting,  chalk,  or  anything  which 
will  prevent  it  from  adhering  to  the  cavity  when  the 
impression  is  taken.  A^Hien  taking  the  impression  of 
a  cavity,  it  is  essential  to  include  in  the  impression  at 
least  a  part  of  the  face  of  the  tooth ;  this  will  act  as  a 


POKCELAIN      FILLINGS  79 

guide,  when  building  up  the  porcelain,  to  obtain  proper 
contour.  When  the  impression  has  been  taken,  plaster 
should  be  poured  into  the  die  cup  of  a  suitable  swager, 
and  while  still  soft,  the  impression  should  be  im- 
bedded in  it  and  allowed  to  remain  until  the  plaster 
has  thoroughly  set,  when  the  wax  can  be  removed. 
Over  this  impression  the  matrix  can  be  swaged,  first 
pressing  it  to  place  and  approximately  fitting  it  by 
pressing  with  cotton,  spunk,  or  other  soft  material, 
after  which  it  can  be  placed  in  the  cylinder  of  the 
swager  and  the  final  swaging  done  with  moldine, 
rubber,  or  with  the  water  bag. 

If  modeling  composition  is  used  as  the  impression 
material,  the  same  general  suggestions  should  prevail 
regarding  the  taking  of  the  impression,  but  cement 
should  be  used  for  making  the  model  in  place  of 
plaster.  Cement  is  harder  than  plaster,  and  for  this 
reason  is  preferred  by  some  who  favor  the  swaging 
method. 

Another  method  of  making  the  matrix  has  been 
described  by  Dr.  A.  E.  Peck,  and  it  is  claimed  by 
many  to  be  superior  to  either  of  the  methods  here- 
tofore described,  for  the  reason  that  it  eliminates  the 
thickness  of  the  matrix  metal  and  provides  for  the 
making  of  an  inlay  which  perfectly  fits  the  cavity. 
Dr.  Peck's  Dr.  Peck  says :  "To  obtain  this  result,  a 
Method  correct  impression  of  the  cavity  must  be 
taken  in  cement.  The  convex  surface  of  the  im- 
pression represents  the  exact  inside  of  the  cavity; 
the  concave  surface  of  a  matrix  swaged  to  fit  this 
also  represents  the  exact  inside  of  the  cavity.  A 
filling  baked  to  this  concave  surface  after  remov- 
ing the  matrix  must  be  a  duplicate  of  the  impres- 
sion, and  if  contraction  and  expansion  have  been  con- 
trolled, must  fit  the  cavity  perfectly." 


80         gilbert's  notes  on  dental  porcelain 

The  teclmic  of  making  a  matrix  by  the  swaging 
method  is  practically  the  same  whether  wax,  model- 
ing composition,  or  cement  is  used  as  the  impression 
material.  A  correct  impression  and  model  of  the 
cavity  is  an  essential,  and  a  perfect  adaptation  of  the 
metal  to  the  impression  or  model  must  be  made  in 
either  case  if  a  perfect  porcelain  filling  is  to  be  the 
result. 

Ash's  The  Ash  Crown  Rubber  Block  Swager  or 

Swager  the  Ash  Inlay  Swager  is  admirably  adapted 
for  the  purpose  of  making  matrices,  their  use  accord- 
ing to  the  claims  of  their  manufacturers  affording  the 
following  advantages : 

"(a)  The  platinum  foil  is  evenly  and  perfectly 
swaged  into  and  around  the  edges  of  the  cavity  by 
means  of  the  hydraulic  pad  in  the  inlay  swager;  an 
unalterable  matrix  is  thus  secured. 

"(b)  Foil  swaged  in  this  way  does  not  alter  in 
shape  during  the  firing  of  the  inlay  because  it  is  free 
from  the  springiness  which  results  from  the  unequal 
pressure  that  is  applied  to  foil  burnished  into  a  cavity 
by  the  hand  method. 

"(c)  It  entirely  does  away  with  the  danger  of 
slightly  altering  the  shape  of  the  matrix,  such  as 
always  attends  the  withdrawal  of  a  matrix  that  has 
been  burnished  into  the  cavity. 

"(d)  Inlays  can  be  prepared  away  from  the 
mouth  without  that  frequent  reference  to  patients 
which  has  hitherto  been  unavoidable. ' ' 

When  a  perfect  matrix  has  been  obtained  by  either 
the  burnishing  or  by  the  swaging  method,  it  should 
be  again  annealed,  after  which  it  is  ready  to  receive 
the  porcelain.  The  various  grades  of  porcelain  now 
found  upon  the  market  are  prepared  ready  for  mix- 
ing, and  it  is  only  necessary  to  select  the  desired 


PORCELAIN     FILLINGS  81 

shades  and  combine  each  with  the  mixing  medium. 
For  this  purpose  water,  alcohol,  and  solutions  of  gum 
tragacanth  have  been  recommended ;  but  clear  water 
alone  is  not  only  all  that  is  necessary,  but  it  is 
superior  to  either  alcohol  or  gum  solutions  for  all 
ordinary  work. 

Application  ^^  ^^  seldom  possible  to  match  the  dentin 
of  the  and  enamel  of  the  natural  tooth  by  using 

Porcelain  ^  single  shade  of  porcelain,  although  there 
are  instances  where  the  results  obtained  by  the  use  of 
one  shade  will  be  found  ''good  enough"  to  meet  re- 
quirements. In  such  cases  a  small  quantity  of  the 
selected  powder  should  be  placed  on  a  clean  slab  of 
glass  or  porcelain,  a  drop  or  more  of  water  added, 
and  the  porcelain  and  water  combined  by  spatulating 
until  it  assumes  the  consistence  of  very  thick  cream. 
Different  grades  of  porcelain  require  to  be  mixed 
differently  owing  to  the  nature  of  the  component 
parts  of  the  porcelains  and  also  to  the  texture  to 
which  each  has  been  reduced,  but  for  general  instruc- 
tions it  is  well  to  say  that  the  mixture  should  assume 
the  consistence  of  thick  cream  or  only  that  degree  of 
fluidity  which  will  permit  it  to  drop  from  the  end  of  a 
brush  or  spatula  and  settle  evenly  over  the  floor  of 
the  matrix. 

When  applying  the  porcelain  to  a  matrix  fitted  to 
the  cavity  of  an  extracted  or  experimental  tooth,  the 
matrix  should  be  laid  in  the  cavity,  the  mixed  porce- 
lain dropped  into  it  from  the  end  of  a  brush  or 
spatula,  and  all  excess  moisture  removed  by  tapping 
the  tooth  and  by  pressing  absorbent  cloth  upon  the 
porcelain. 

The  amount  of  porcelain  which  should  be  placed 
in  the  matrix  for  the  first  firing  depends  upon  the 
form  and  depth  of  the  cavity  and  the  quality  of  the 

6 


82         gilbert's  notes  ox  dental  porcelain 

porcelain  which  is  being  used ;  but  generally  speaking 
the  matrix  should  be  half-filled,  and  then  before  plac- 
ing it  in  the  furnace  the  porcelain  should  be  scored 
in  sections  by  using  a  sharp  instrument,  this  being 
done  to  control  the  shrinkage  and  prevent  it  from  dis- 
torting the  form  of  the  matrix. 

The  Initial  Having  partially  filled  the  matrix  with  the 
Firing  mixed    porcelain,    dried    and    scored    the 

same,  the  matrix  and  its  contents  can  be  removed 
from  the  cavity,  placed  upon  a  fire-clay  or  platinum 
pan  the  bottom  of  which  has  been  previously  covered 
with  silex,  and  the  whole  then  placed  in  a  position 
near  the  opening  of  the  furnace,  where  it  can  be 
gradually  heated  before  being  subjected  to  the  firing 
temperature. 

Two  Methods  There  are  two  distinct  methods  of  building 
of  Building  up  an  inlay  of  porcelain,  and  as  instructions 
Inlays  fQ^  firing  differ  according  to  the  method 

used,  it  will  be  necessary  to  refer  at  this  point  to  the 
use  of  a  single  grade  of  porcelain  throughout  the  con- 
struction and  to  the  combination  of  twa  or  more 
grades  having  different  firing  temperatures. 

It  is  claimed  by  some  experimenters  that  all  porce- 
lain must  be  entirely  glazed  before  the  maximum 
amount  of  shrinkage  can  take  place,  while  others 
claim  that  the  shrinkage  takes  place  before  the  porce- 
lain reaches  the  hard-biscuited  condition.  It  is  due  to 
this  difference  of  opinion  that  the  two  methods  of 
building  up  an  inlay  are  in  vogue. 
Inlays  of  When  one  grade  of  porcelain  is  to  be  used 
One  for  the  entire  inlay,  the  porcelain  should 

Porcelain  ^Qt  i^^  subjected  to  a  temperature  which  will 
glaze  the  same  until  the  final  firing,  but  it  should  be 
subjected  to  a  temperature  which  will  produce  shrink- 
age ;  and  this  condition  is  recognized  when  the  porce- 


PORCELAIN    FILLINGS  83 

lain  is  hard,  but  not  glossy,  and  the  mass  seems  to  be 
covered  with  minute,  shining  particles.  If  an  inlay 
consisting  of  one  grade  of  porcelain  be  subjected  only 
to  a  ''hard-biscuit"  fire  during  the  initial  application 
of  the  porcelain,  then  the  final  layer  of  porcelain  can 
be  perfectly  glazed  without  overfiring  the  porcelain 
beneath.  After  the  initial  firing  of  an  inlay,  the  ma- 
trix can  be  removed  from  the  muffle  of  the  furnace 
without  any  care  being  taken  to  cool  it,  an  additional 
quantity  of  porcelain  mixed,  and  the  second  layer 
placed  in  the  matrix,  using  great  care  to  fill  all  the 
shrinkage  cracks  and  interstices  made  by  the  first 
firing. 

If  enough  porcelain  is  added  to  fill  the  matrix,  the 
second  "hard-biscuit"  fire  should  result  in  the  filling 
of  all  cracks  and  leave  an  even,  rough  surface  for  the 
addition  of  the  third  and  generally  the  final  fire. 
When  placing  the  final  layer  of  porcelain  in  the  ma- 
trix, it  should  be  applied  evenly  and  made  flush  with 
the  margins,  taking  care  not  to  overlap  the  margins, 
but  to  make  a  fulness  which  will,  when  glazed,  make  a 
strong,  sharp  edge. 

Inlays  of  Inlays  made  from  more  than  one  grade  of 
Two  porcelain  are  to  be  built  up  in  the  manner 

Porcelains  just  described,  but  in  the  firing  of  each 
layer  the  temperature  is  to  be  carried  sufficiently  high 
to  glaze  the  porcelain. 

The  first  layer  should  be  of  porcelain'  the  firing 
point  of  which  is  considerably  higher  than  the  firing 
point  of  that  which  is  to  be  used  for  the  second  layer, 
and  the  porcelain  used  for  the  third  layer  should  have 
a  firing  point  considerably  lower  than  that  used  for 
the  second  layer. 


84 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


SHADING  THE  INLAY 

The  method  given  above  for  making  a  solid  color 
inlay  should  be  followed  in  the  making  of  a  shaded 
inlay,  but  in  place  of  using  the  same  shade  of  porce- 
lain throughout  different  shades  should  be  selected 
and  so  applied  to  the  matrix  as  to  give  the  desired 
shade  effect  in  the  finished  inlay. 

It  is  impossible  to  lay  down  any  definite  directions 
for  the  distribution  of  shades  in  porcelain  work,  but  it 
is  essential  to  know  that  natural  shade  effects  in 
porcelain  can  only  be  produced  by  blending  two  or 
more  shades  in  a  mechanical  and  artistic  manner. 

Suppose  an  inlay  is  indicated  to  restore  the  ap- 
proximal  side  and  part  of  the  incisal  edge  of  an  ante- 
rior tooth.     (Fig.  61.) 

Fig.  61 


Upon  careful  examination  of  the  remaining  por- 
tion of  the  natural  tooth  we  find  that  it  is  yellow  at 
the  neck  and  gray  at  the  cutting  edge,  and  that  there 


POECELAIN      FILLINGS  85 

Fig  G2     ^^  ^  gradual  blending  of  these  two  colors 
throughout  the  body  of  the  tooth. 
11  To  make  an  inlay  for  such  a  tooth,  the 

following  procedure  is  indicated:  With 
the  aid  of  a  shade  guide,  select  the  tints 
of  yellow  and  gray  found  in  the  natural 
tooth;  mix  each  of  these  porcelains  with 
water  on  separate  mixing  slabs  or  on  one 
slab  which  is  large  enough  to  keep  the 
two  mixings  entirely  separate.  Place  the 
mixed  shade  of  yellow  porcelain  in  the 
matrix ;  settle  it  in  place  by  chattering  the 
matrix  with  the  side  of  a  mixing  and 
carving  tool  (Fig.  62),  or  by  tapping  with 
the  side  of  some  other  instrument.  Ab- 
sorb the  moisture  as  it  appears  on  the  sur- 
face, and  when  the  porcelain  in  the  matrix 
is  of  a  consistence  similar  to  cheese,  carve 
and  build  it  up  as  desired.  At  this  stage 
of  the  work  the  initial  firing  should  be 
made,  carrying  the  temperature  only  to 
the  ^'hard  biscuit"  if  one  grade  is  being 
used,  or  to  a  glaze  if  several  grades  of 
porcelain  are  being  used.  Yellow  porce- 
lain should  be  used  to  fill  in  the  shrinkage 
cracks  for  the  second  fire,  and  if  necessary 
it  should  also  be  added  at  the  neck  and 
again  blended  toward  the  cutting  edge,  as 
shown  in  Fig.  63.  When  properly  dried, 
the  inlay  should  again  be  placed  in  the 
muffle  of  the  furnace  and  subjected  to  the 
proper  temperature,  according  to  the 
method  used.  In  the  final  application  of 
porcelain  the  gray  shade  must  be  used; 
this  is  placed  in  the  matrix,  filling  it  flush 


86         gilbert's  notes  on  dental  porcelain 

with  the  margins,  and  when  dried  the  inlay  should 
be  again  placed  in  the  furnace  and  subjected  to  a  tem- 
perature which  will  produce  the  desired  amount  of 
glaze.  An  inlay  constructed  in  the  manner  described 
will  be  found  to  approximate  the  blending  found  in 
the  natural  teeth ;  in  fact,  it  is  simply  duplicating  in 
porcelain  what  nature  did  in  distributing  the  shades 
of  natural  teeth.  This  process  of  blending  colors  to 
produce  shade  in  porcelain  has  been  followed  by  arti- 
ficial tooth  manufacturers  for  many  years,  and  it  is 
the  only  way  in  which  the  individual  porcelain  worker 

Fig.  63 
A      


v^ 

'B 

can  hope  to  solve  the  shade  question  in  porcelain 
work.  Modifications  of  this  method  will,  of  course, 
be  necessary.  Sometimes  the  worker  will  be  obliged 
to  make  his  own  admixtures  of  the  manufacturer's 
ready-made  shades  in  order  to  obtain  the  proper 
underlying  colors  to  begin  with ;  in  some  cases  he  will 
be  obliged  to  mechanically  blend  more  than  two  colors 
to  produce  a  desired  shade  effect ;  but  if  the  principle 
of  blending  colors  to  produce  shade  is  once  under- 
stood, the  technic  for  making  the  special  inlay  will  be 
apparent  to  the  artist  in  this  work. 

CEMENTING  THE  INLAY 

"When  the  inlay  is  completed,  remove  the  matrix 
by  first  loosening  it  around  all  the  edges  with  the 
point  of  an  excavator,  and  then  tease  it  from  the 
porcelain,  working  it  toward  the  center  of  the  inlay. 


POKCELAIN     FILLINGS  87 

If  the  inlay  be  dipped  in  water  after  the  edges  have 
been  started,  it  will  aid  in  the  separation  of  inlay  and 
matrix ;  but  care  must  be  taken  to  see  that  the  inlay 
is  cool  before  this  is  done,  otherwise  the  water  will 
cause  checking.  When  the  matrix  has  been  entirely 
removed,  try  the  inlay  in  the  cavity,  and, if  the  adapta- 
tion is  correct,  prepare  the  inlay  for  its  retention  in 
the  cavity.  This  may  be  done  by  etching  the  cavity 
side  of  the  inlay  with  hydrofluoric  acid  or  by  cutting 
small  grooves  with  a  thin  diamond  disk  (Fig.  64), 

Fig.  64 


keeping  it  wet  so  as  to  facilitate  cutting  and  to  pre- 
vent heating  of  the  porcelain,  which  would  cause 
cracks.  The  inside  of  the  cavity  should  also  be 
roughened  or  undercut  so  that  the  cement  can  take 
a  firm  hold  on  the  tooth,  thus  strengthening  the  attach- 
ment of  the  inlay.  Cement  is  the  best  material  at  our 
disposal  for  making  the  attachment  of  the  inlay  to 
the  tooth,  and  this  should  be  of  a  quality  which  will 
practically  set  in  say  twenty  or  thirty  minutes.  Mix 
the  cement  to  a  point  where  it  is  just  fluid,  and  with  a 
small  spatula  (Fig.  65)  fill  the  undercuts  in  both  inlay 
and  cavity ;  then,  placing  the  inlay  in  the  cavity,  press 
one  wall  in  advance  of  the  others  so  that  the  air  will 
be  excluded.  Keep  the  inlay  under  pressure  until  the 
cement  is  quite  hard.  Allow  the  surplus  to  remain 
around  the  edges  without  disturbance  until  the  ce- 
ment is  hard,  then  remove,  not  by  chipping  with  an 
excavator,  but  by  the  use  of  strips  or  paper  disks. 
When  practical,  it  is  better  to  leave  this  until  the 
next  day. 


88         gilbert's  notes  on  dental  porcelain 

Fig.  65 


No.  13 


No.  13  A 


CHAPTER   VII 


SHADING  PORCELAIN 

The  proper  shading  of  an  inlay  or  crown  calls  for 
the  exercise  of  artistic  skill,  in  developing  and  em- 
ploying which  the  worker  in  porcelain  will  find  much 
pleasure  and  remuneration.  The  mixing  of  colors  to 
produce  tooth  shades  is  not  to  be  learned  from  read- 
ing, but  must  come  from  the  hard  knocks  of  experi- 
ence. Diversified  tints  of  unlimited  variety  can  be 
produced  by  altering  the  proportions  of  the  basal 
colors,  and  by  the  proper  blending  of  the  desired  tints 
very  natural  effects  can  be  produced.  The  basal  color 
of  nearly  all  teeth  is  light  yellow,  and  it  will  be  found 
very  practical  to  use  this  color  in  building  up  that 
portion  of  a  crown  which  corresponds  to  the  dentin 
Unnatural-  ^^  ^^^®  natural  organ.  The  unnatural  ap- 
looking  pearance  of  many  artificial  crowns  is  due  to 
rowns  ^YiQ  fact  that  they  are  of  one  uniform  color, 
and  not  of  two  or  three  shading  into  each  other,  as 
we  find  in  the  natural  teeth. 

Since  the  advent  of  high-grade  porcelain  in  the 
requisite  colors  there  has  been  no  excuse  for  solid- 
color  crowns,  for  it  is  now  possible  to  closely  approxi- 
mate the  natural  teeth  in  their  varying  shades,  even 
to  the  staining  of  fissures  and  streaking  of  enamel. 

The  best  way  for  a  beginner  in  porcelain  work, 
tlierefore,  is  to  experiment  in  the  mixing  and  fusing 
of  colors  before  he  attempts  the  construction    of  a 


90 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


practical  inlay  or  crown.  This  work  can  be  made 
immediately  profitable  in  experience,  for  he  will  need 
a  set  of  sample  shades  made  from  the  materials  he  is 
to  work  with.  He  will  find  greater  satisfaction  in 
working-  to  shades  of  his  own  compounding  than  with 
any  fixed  samples  of  mixes  supplied  by  the  manu- 
facturers of  the  material.  Of  course,  in  making  these 
buttons  he  will  need  to  note  carefully  the  exact  pro- 
portions in  each  experiment.  He  will  thus  have  an 
invaluable  record,  and  every  experiment  will  serve  as 
a  guide  in  his  future  practical  work;  the  failures 
advising  him  what  to  avoid,  the  successes  pointing 
the  clear  way  to  useful  practical  results. 
Making  Shade  A  practical  method  of  making  new  shades 
Samples  from  the  powders  furnished  by  the  manu- 
facturers is  to  carve  a  suitable  form  in  plaster,  wood, 
or  metal,  and  from  such  a  form  make  a  mold  with 
Melotte's  metal.     (Fig.  66.)     By  the  use  of  such  a 

Fig.  6C 


mold  new  shade  forms  of  uniform  shape  and  size  can 
be  made. 

Weigh  out  varying  proportions  of  the  different 
colored  powders  and  mix  with  water  to  the  consist- 
ence of  dough,  then  oil  the  mold  and  press  it  into  the 


SHADING     PORCELAIN  91 

mixed  porcelain.  If  the  mold  has  been  properly  made, 
an  imprint  of  the  desired  form  will  be  made  in  the 
porcelain,  and  this  when  properly  trimmed  and  fired 
will  record  the  new  shade  so  produced. 

Care  should  be  taken  to  record  the  various  mix- 
tures so  that  they  may  be  duplicated  at  any  time.  The 
keeping  of  such  records  may  be  made  in  this  way — 
using  the  letters  of  The  S.  S.  Wliite  Dental  Mfg.  Co.'s 
porcelain  to  illustrate :  Three  parts  of  A  added  to  two 
parts  of  B  will  produce  a  new  shade,  which  can 
be  designated  as  No.  1,  or  by  any  name  desired,  and 
can  be  recorded  thus :  3  A  +  2  B  —  No.  1.  It  will  be 
observed  that  by  making  shades  as  here  suggested 
there  is  no  end  to  the  shades  that  can  be  produced. 
To  illustrate  still  further:  A  is  gray,  while  G  is 
white  or  colorless,  used  principally  as  a  modifier  to 
get  gradations  of  other  colors : 

Make  mixtures  of  varying  proportions  of  A  and 
G,  thus :  9  A  +  1  G,  then  another  mix  9  A  +  2  G,  and 
so  on.  By  combining  each  of  the  other  shades  in 
this  way  with  G  two  hundred  and  fifty  gradations  will 
be  produced,  and  this  is  only  the  beginning  of  the 
possible  combinations. 

The  method  just  described  answers  very  well  if 
the  texture  of  the  porcelain  is  coarse  like  that  of  the 
Allen  and  Close  bodies ;  but  if  the  texture  is  fine,  like 
that  of  most  porcelain  now  used,  there  will  be  more  or 
less  difficulty  in  removing  the  porcelain  from  the 
mold.  This  difficulty  is  due  to  the  close  adaptation  of 
the  fine  particles  of  porcelain. 

When  making  new  shade  samples  from  a  fine 
texture  porcelain,  the  same  mold  (Fig.  66)  can  be 
used,  but  the  method  of  using  must  be  changed.  In 
place  of  mixing  the  porcelain  with  ordinary  water  and 
pressing  the  mold  into  the  porcelain  it  is  advisable  to 


92 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


use  gum  water  and  press  the  porcelain  into  the  mold. 
The  mold  containing  the  porcelain  can  then  be  placed 
in  a  suitable  ladle  and  melted,  thus  delivering  the 
porcelain  shade  sample  in  a  perfect  condition.  An- 
other mold  can  be  made  in  a  few  minutes  by  flowing 
metal  over  the  original  metal  form. 
Pouring  Another  method  of  making  individual  shade 
Method  samples  may  be  described  as  follows :  A 
metal  mold,  consisting  of  four  parts,  can  be  readily 
constructed  so  that  the  mixed  porcelain  can  be 
poured  or  dropped  into  it  and  the  mixing  medium 
absorbed.  Fig.  67  represents  the  front  face  of  such  a 
mold;  Fig.  68,  the  pouring  gate;  Fig.  69,  the  part 

Fig.  67 


which  carries  the  pins  for  making  the  holes  in  the 
finished  shade  samples ;  Fig.  70,  the  back  face,  which 
holds  the  absorbent  plaster.  To  make  sample  pieces 
in  a  mold  of  this  description  it  is  necessary  to  thor- 
oughly oil  all  working  faces,  hold  the  parts  together 
with  a  clamp  of  some  kind,  and  then  drop  the  thinly 
mixed  porcelain,  drop  by  drop,  into  the  mold,  being 
careful  not  to  clog  up  the  opening.  When  the  mold  is 
filled,  put  it  aside  until  the  porcelain  sets ;  then  open 
the  mold  and  gently  remove  the  porcelain  castings. 


SHADING     PORCELAIN 


93 


When  the  plaster  becomes  saturated  with  the  mixing 
fluid,  knock  it  out  of  the  frame  and  pour  a  new  back. 
Some  porcelains,  like  Ash  &  Sons '  High-  and  Low- 
Fusing,  S.  S.  White  Dental  Mfg.  Co.'s  Medium-Fus- 
ing, and  Brewster's  Enamel,  are  easily  handled  and 

Fig.  68 


Fig.  69 


Fig.  70 


Fig.  71 


seem  to  be  particularly  adapted  for  use  by  the  pour- 
ing method;  while  other  i^orcelains,  like  the  S.  S. 
White  Dental  Mfg.  Co.'s  High-Fusing  Porcelain, 
Close,  Allen,  and  Block  Bodies,  are  better  adapted 
for  use  in  the  pressing  method. 


94         gilbert's  >:otes  ox   dental  porcelain 

Something  With  hundreds  of  shades  from  which  to 
Shades^*"  select,  the  possibilities  of  obtaining  a  de- 
Required  sired  result  will  be  greatly  increased,  but  it 
must  not  be  supposed  that  this  variety  will  be  all  that 
is  necessary  to  secure  shades  as  they  are  found  in 
the  natural  tooth. 

If  a  section  of  a  natural  central  incisor  be  ex- 
amined (Fig.  72),  it  will  be  observed  that  the  dentin 
which  forms  the  bulk  of  the  tooth  is  one  color  and  the 
enamel  which  covers  the  dentin  is  another  color. 
Furthermore,  the  enamel  is  thinnest  at  the  neck  of  the 
tooth,  but  gradually  increases  in  thickness  as  it  ap- 
proaches the  cutting  edge.  Here  is  a  lesson  direct 
from  nature,  and  one  which  the  manufacturers  of 
artificial  teeth  have  learned  and  put  into  application. 
The  shades  of  factory-made  porcelain  teeth  are  not 
obtained  by  using  a  single  shade  of  porcelain,  as 
man}^  so-called  porcelain  workers  suppose,  but  the}'' 
are  made  by  employing  two  distinct  shades  of  porce- 
lain and  blending  them  to  produce  natural  shade 
effects.    (Fig.  73.)  - 

Fig.  72  Fig.  73 


When  making  artificial  porcelain  teeth,  the  molder 
places  the  enamel  or  light  shade  in  the  labial  face  of 
the  mold,  blends  it  with  a  hand  tool,  leaving  an  open 
space  at  the  neck.    A  tip  of  enamel  is  also  placed  at 


SHADING   PORCELAIN  '  95 

the  cutting  edge  in  the  lingual  face  of  the  mold.  The 
body  or  dark  shade  of  porcelain  is  placed  in  that  por- 
tion of  the  lingual  face  of  the  mold  not  occupied  by 
the  tip  of  enamel,  and  the  two  parts  of  the  mold 
are  then  put  together  and  the  body  and  the  enamel 
blended  by  putting  the  mold  under  pressure. 

The  practitioner  who  expects  to  obtain  natural 
effects  in  either  crowns  or  inlays  must  follow  in  a 
general  way  the  methods  used  by  tooth  manufac- 
turers. If  the  underlying  color  of  a  crown  is  yellow 
and  the  enamel  a  yellowish  white,  select  a  yellow 
porcelain  to  build  up  that  portion  of  the  crown  which 
corresponds  to  the  dentin  in  the  natural  tooth  and 
then  cover  this  yellow  shade  with  a  layer  of  the 
yellowish  white  or  white  shade.  The  same  thing 
applies  to  small  inlays  even  when  the  amount  of 
porcelain  would  appear  too  small  to  require  more 
than  one  color.  This  blending  of  two  or  more  shades 
is  the  correct  solution  of  the  shade  problem,  and  it 
must  be  observed  if  the  best  results  are  desired. 


CHAPTEE    VIII 


MINERAL  STAINS 

The  observant  student  will  recognize  the  fact  that 
shades  as  well  as  the  form  of  human  teeth  vary 
greatly  in  the  same  denture.  Only  on  rare  occasion 
do  we  see  dentures  in  which  the  pairs  of  each  class 
are  true  mates.  The  left  central  is  seldom  like  the 
right  central ;  there  is  always  a  difference  in  the  form 
of  the  laterals,  and  so  on,  each  tooth  in  the  denture 
having  its  individuality. 

The  ravages  of  nature  have  their  effect  upon  the 
individual  tooth.  Mastication,  lack  of  occlusion,  dis- 
ease, etc., — each  does  its  part  in  wearing  and  shaping 
the  teeth  until  there  is  little  more  than  type  resem- 
blance existing  between  pairs  of  teeth  which  were  at 
one  time  closely  mated  in  form.  At  the  time  of  life 
when  artificial  teeth  become  a  necessity,  the  natural 
organs  have  been  mutilated  to  such  an  extent  that 
symmetry  is  destroyed.  It  is  as  unreasonable  as  it  is 
undesirable  to  expect  manufacturers  to  make  artificial 
teeth  which  would  be  in  accord  with  the  innumerable 
Individuality  stages  of  wear  and  discoloration  found  in 
in  Teeth  the  natural  teeth.  Individual  cases  requir- 
ing artificial  substitutes  for  the  natural  organs  must 
always  require  individual  effort  upon  the  part  of  the 
dentist  if  he  wishes  to  restore  harmony  of  the  fea- 
tures. With  the  aid  of  a  dental  engine  and  an  abra- 
sive wheel,  the  dentist  may  age  and  mutilate  artificial 

96 


MINEEAL    STAIKS  97 

teetli  just  as  effectively  as  nature  by  her  methods 
ages  and  mutilates  the  natural  organs.  The  shades 
of  individual  teeth  which  enter  into  the  make-up  of  a 
natural  denture  are  by  no  means  uniform ;  they  vary 
greatly  in  depth  of  color,  and  if  the  individual  shade 
is  carefully  ' '  taken ' '  it  will  be  found  that  six  or  seven 
shades  or  variations  of  the  same  general  shade  will 
be  found  in  a  single  denture.  As  a  rule,  the  teeth  of 
artificial  dentures  are  selected  at  the  dental  depots 
and  used  as  they  are  purchased.  If  a  full  upper  set 
is  required,  a  set  of  fourteen  teeth  all  of  the  same 
shade  is  used.  This  is  wrong,  and  such  practice  par- 
tially accounts  for  the  incongruous  effects  which  are 
noticeable  in  the  mouths  of  those  wearing  artificial 
teeth.  Deposits  and  stains  also  help  to  break  up  the 
uniformity  of  shade,  and  to  a  certain  extent  these 
stains  must  be  reproduced  in  the  artificial  dentures, 
especially  in  partial  cases  where  several  natural 
teeth  remain  to  act  as  examples  of  comparison  be- 
tween the  real  and  the  false.  Modifications  which 
can  be  made  in  a  single  form  of  factory-made  teeth 
are  only  limited  by  the  knowledge  and  skill  of  the 
dentist.  The  abrasive  wheel  alone  can  be  made  to 
effect  variations  in  age  and  arrangement  which  will 
destroy  the  identity  of  the  original  form,  and  when 
we  consider  the  changes  made  practicable  by  the  use 
of  stains,  the  possibilities  of  copying  nature  are 
indeed  great. 

To  Effect  It  is  so  simple  to  make  changes  in  the  manu- 
Changes  f  actured  teeth  that  the  beginner  in  this  class 
of  artistic  prosthesis  will  be  surprised  at  the  result  of 
his  efforts.  As  an  example  of  what  may  be  accom- 
plished by  the  use  of  the  abrasive  wheel,  take  a  few 
sets  of  anterior  teeth  all  made  from  the  same  mold ; 
allow  one  of  the  sets  to  remain  untouched  for  the 


98 


GILBERT  S    NOTES    ON    DENTAL    PORCELAIN 


purpose  of  comparison,  but  take  the  others  and  grind 
them  to  represent  the  natural  teeth  of  individuals 
whom  you  see  every  day. 

Carry  the  object  lesson  a  little  further  by  chang- 
ing another  set  with  the  grindstone  and  then  mount- 
ing them  upon  a  base-plate  of  wax,  changing  the  ar- 
rangement of  the  anterior  teeth,     (Figs.  74  to  80.) 

Fig.  74  represents  the  sanguineous  temperament. 

Fig.  74 


Mold  213 


as  to  the  shape,  outline,  and  alignment  of  the  teeth, 
and  the  general  form,  ''well  proportioned,  abounding 
in  curved  or  rounded  outline;  cusps  rounding." 
In  Fig.  75  there  is  a  strong  prominence  of  the  cen-- 


Fig.  75 


Mold  213 


tral  incisors,  with  the  laterals  inclined  forward  and 
standing  behind  the  centrals.  The  arch  is  somewhat 
contracted  from  the  cuspids  forward. 


MINERAL     STAINS 


99 


In  Fig.  76  tliere  is  less  prominence  of  the  centrals ; 
the  laterals  pitched  forward  enough  to  overlap  the 
centrals  at  the  tip  ends. 

Fig.  76 


Mold  213 


In  Fig.  77  the  centrals  are  rotated  toward  the 
median  line  and  depressed  at  the  incisai  ends ;  laterals 
rotated  to  expose  their  anterior  approximal  edges, 
with  a  pitch  toward  the  centrals. 


100 


(4ILBERT  S    NOTES    ON     DENTAL    PORCELAIN 


Fig.  78  shows  a  directly  opposite  condition  from 
that  seen  in  Fig.  77.  The  centrals  are  rotated  to  form 
a  V-shaped  or  pointed  arch,  and  with  the  laterals 
pitching  toward  the  facial  line;  the  cuspids  are  so 
placed  as  to  narrow  the  arch  at  the  point  of  their 
insertion. 

Fig.  78 


Mold  213 
Fig.  79 


Mold  213 


Fig.  79  shows  a  common  alignment  of  the  incisors, 
the  laterals  pitched  slightly  toward  the  centrals.    The 


MINERAL     STAINS 


101 


occlusal  ends  of  the  teeth  are  ground  a  little  to  show 
slight  wear,  as  at  the  age  of  twenty-five  or  thirty 
years. 


Fig.  80 


Mold  213 

Fig,  80  is  an  example  showing  considerable  wear, 
representing  the  condition  of  the  teeth  at,  say,  fifty 
years.    The  teeth  are  regular  in  alignment. 

It  will  be  seen  from  the  illustrations  that  arrange- 
ment and  grinding  will  do  much  to  disguise  the  artifi- 
cial effect  of  porcelain  teeth,  and  when  mineral  stains 
are  used  in  connection  with  the  grinding  and  arrange- 
ment, the  disguise  may  be  made  nearly  if  not  entirely 
complete. 

The  Mineral  stains,  porcelain  enamels,  or  oil 

Stains  colors,  as  they  are  called,  according  to  the 

manufacturer  who  makes  them,  are  pigments  made 
for  the  purpose  of  changing  the  shade  or  producing 
artistic  effects  upon  porcelain  teeth  or  inlays.  Like 
the  various  porcelain  compounds  found  upon  the 
market,  these  stains  vary  in  character  and  working 
qualities  according  to  the  formulas  and  processes  em- 
ployed in  their  manufacture,  and  what  has  been  pre- 
viously said  regarding  the  qualities  of  porcelain  ap- 
plies with  equal  force  to  mineral  stains — that  is,  the 
only  way  to  become  familiar  with  the  working  quali- 
ties of  each  make  is  by  actual  experiment. 

The  principal  practical  application  of  stains  will 
be  found  in  producing  the  imitation  of  wear,  the  aging 


102 


GILBERT  S    NOTES    OX     DENTAL    PORCELAIN 


"which  is  shown  by  stains  and  deposits  in  the  fissures 
of  the  bicuspids  and  molars  and  the  cutting  edges  of 
the  incisors,  and  in  the  general  darkening  of  the 
shades  of  the  teeth. 

Other  opportunities  for  their  employment  will  be 
found  in  the  construction  of  crowns  and  inlays  made 
from  high-fusing  porcelains.  In  this  particular  ap- 
plication they  can  be  used  either  as  overglaze  or  as 


underglaze  colors. 


Fig.  81 


Practical  The  stains  are  supplied  in  basal  colors — 
Application  white,  gray,  blue,  brown,  yellow,  green, 
and  pink  or  gum  color.  (Fig.  81.)  In  some  cases  some 
of  the  basal  colors  may  be  used  alone,  but  for  general 
application  it  will  be  necessary  to  make  admixtures 
in  order  to  produce  the  great  variety  of  shades,  stains, 
and  discoloration s  found  upon  the  surfaces  of  natural 


MINERAL     STAINS  103 

teeth.  To  thoroughly  learn  the  effect  of  combina- 
tions of  these  colors  with  one  another  and  with  the 
tone  color  of  the  teeth  which  are  to  be  modified,  some 
little  experimental  work  is  necessary  in  order  to  be- 
come familiar  with  their  behavior.  In  fact,  it  is  al- 
Make  ways  safer  to  make  a  provisional  or  pre- 

Trials  liminary  test  of  each  case  as  it  occurs.    A 

discarded  tooth  will  answer  very  well  as  a  test  piece. 
Paint  on  a  little  of  the  color  or  combination  which  ap- 
pears to  be  right  and  fire  it  to  see  whether  the  proper 
tint  is  brought  out.  This  point  should  be  assured 
before  the  color  is  laid  on  the  tooth  to  be  shaded.  It 
takes  only  a  few  minutes  to  make  this  trial  and  it  will 
many  times  prevent  serious  error. 
•  Specific  direction  for  the  production  of  desired 
effects  cannot  be  given  on  account  of  the  difference 
in  quality  of  the  different  makes  of  stain,  but  general 
directions  for  producing  some  of  the  desirable  effects 
may  be  given  as  follows :  If  the  tone  of  the  tooth  is 
yellow,  the  addition  of  brown  will  first  darken  the 
yellow,  then,  as  more  and  more  is  added,  bring  out 
a  more  and  more  decided  brown.  If  the  tone  is  blue 
or  gray,  brown  at  first  merely  deepens  it,  but  on  the 
addition  of  a  considerable  quantity  produces  a  de- 
cided brown.  A  combination  of  green  with  brown 
will  give  a  natural-looking  stain  similar  to  that  found 
upon  the  teeth  of  inveterate  smokers.  Natural  cut- 
ting edge  effects  may  be  obtained  by  using  either 
gray  or  blue  as  an  underglaze  color,  i.  e.,  after  apply- 
ing and  firing  the  color,  cover  the  same  with  the  color- 
less low-,  medium-,  or  high-fusing  porcelain  and 
Specific  again  fire.  For  representing  the  wear  of 
Uses  mastication,  the  teeth  can  be  ground  and  the 

cutting  edges  and  fissures  stained  with  the  brown. 
White  spots  frequently  seen  in  the  enamel  of  natural 


104       Gilbert's  notes  ox  dental  porcelain 

teeth  can  be  imitated  hj  applying  a  thin  layer  of 
white.  Defects  in  the  enamel,  such  as  pits  or  grooves, 
can  be  imitated  by  drilling  the  enamel  surface  of  a 
tooth  and  staining  with  the  desired  color.  The  pink 
or  gum  color  will  be  found  very  useful  in  covering- 
platinum  bands  which  are  exposed  below  the  gum 
line,  also  in  coloring  that  portion  of  an  inlay  or 
crown  which  must  match  the  cervical  border  of  ad- 
joining teeth. 

Before  attempting  to  apply  the  stains,  the  teeth 
should  be  made  perfectly  clean  and  dry.  If  they  are 
to  be  ''aged"  they  should  be  set  up,  articulated,  and 
ground  upon  the  cutting  edges  and  articulating  sur- 
faces, then  removed  one  by  one  and  stained. 

In  applying  the  stain  it  is  important  to  mix  the 
material  until  it  works  smoothly  and  to  a  consistence 
which  will  permit  it  to  be  used  after  the  manner  of 
paint.  When  so  mixed,  the  stains  may  be  applied 
with  a  small,  pointed  camel 's-hair  pencil,  and  then 
distributed  over  the  surfaces  of  the  teeth  by  means 
of  the  fingers  or  a  stippling  brush.  If  a  wavy,  granu- 
lated effect  is  desired,  the  material  should  be  applied 
rather  thick;  but  as  generally  required,  it  should  be 
laid  on  very  evenly  and  in  thin  laj^ers,  thus  producing 
a  suggestion  of  color  rather  than  a  decided  effect. 

In  cases  calling  for  a  decided  blue  at  the  cutting 
edge,  a  milk  spot  in  the  labial  surface,  or  the  effect  of 
exposed  dentin,  it  is  advisable  to  make  a  recess  in  the 
enamel  of  the  tooth  with  a  diamond  disk  or  drill  and 
then  fill  this  recess  with  the  stain. 
Firing  the  Any  good  dental  furnace  capable  of  firing 
Stains  the  block  bodies  or  high-fusing  porcelains 

will  serve  the  purpose  for  permanently  "fixing"  all 
the  stains,  and  some  of  them  may  be  fixed  with  the 
gas  blowpipe.     There  is  quite  a  difference  in  the 


MINERAL     STAINS 


105 


AH  Stains  glazing  point  of  the  different  manufac- 
Not  Alike  turers '  product.  Some  of  the  stains  can  be 
fixed  at  a  very  low  temperature  and  vet  withstand  a 
liigh  temperature ;  others  require  a  liigli  temperature 
to  properly  glaze  and  fix  them,  and  then  will  stand 
very  little  excess  heat  without  losing  their  color. 

The  electric  furnace  can  be  depended  upon  to  fire 
even  the  very  high-fusing  stains,  and  is  preferable  for 
the  work  because  of  its  easy  control.  The  teeth 
to  be  fired  should  be  placed  upon  a  tray  made  of 
platinum  or  of  fire  clay,  the  pins  of  the  teeth  rest- 
ing upon  the  tray,  and  then  tray  and  teeth  should  be 
placed  on  top  of  the  furnace,  where  they  can  be  made 
quite  warm  before  attempting  to  place  them  in  the 
muffle.  Great  care  must  be  taken  to  thoroughly  heat 
artificial  teeth  before  subjecting  them  to  high  tem- 
peratures ;  therefore  it  is  advisable  to  have  the  tem- 
perature of  the  muffle  either  cool  or  else  very  low  when 
teeth  are  to  be  stained.  After  the  teeth  have  been 
made  thoroughly  warm,  the  temperature  can  be  grad- 
ually raised  until  the  glazing  point  of  the  stain  has 
been  reached,  when  the  heat  should  be  reduced,  and 
when  cool  enough  the  teeth  can  be  removed.  Some- 
times the  stains,  while  producing  natural  color  effects, 
have  a  tendency  to  produce  an  unnatural  glossy  ap- 
pearance in  the  enamel;  when  this  occurs  it  can  be 
easily  remedied  by  brushing  the  tooth  with  pumice 
stone. 

AVhen  properly  treated  with  a  good  qualit)^  stain, 
artificial  teeth  can  be  subjected  to  all  the  necessary 
laboratory  manipulations  required  in  mounting  and 
finishing,  and  they  will  withrstand  all  practical  use 
in  the  mouth.  The  accompanying  illustrations  will 
suggest  changes  which  can  be  made  in  tlie  appearance 
of  dentures  containing  stained  teeth. 


106       gilbert's  notes  on  dental  porcelain 


Fig.  82 


Fig.  83 


MINERAL     STAINS 


107 


Fig.  82  illustrates  one-half  of  a  set  of  twenty- 
eight  plain  rubber  teeth  as  sold  by  the  manufacturer. 

Fig.  83,  a  and  b,  show  the  masticating  surfaces  of 
this  set  of  teeth  after  they  have  been  ground  to  proper 
occlusion  and  stained  to  represent  natural  defects. 

Fig.  84  represents  the  same  teeth  anatomically 
articulated. 

Fig.  84 


Notice  the  changes  made  in  the  finished  dentures 
by  comparing  Fig.  84  with  the  original  teeth  as  pro- 
vided by  the  manufacturer. 


CHAPTER    IX 


FURNACES 


The  furnace  required  for  the  firing  of  dental 
porcelains  depends  largely  upon  the  grade  of  porce- 
lain used,  the  facilities  for  installing  a  furnace,  and 
the  preferences  of  the  worker.  If  block  bodies  are 
to  be  fired,  the  Revelation  Dental  Furnace  (Fig.  85), 

KiG.  85 


made  by  H.  J.  Caulkins,  of  Detroit,  is  by  all  means 
desirable;  in  fact,  it  is  the  most  practical  furnace 
on  the  market  for  all-around  porcelain  work.    Block 

108 


FURNACES  109 

bodies  require  high  temperatures  to  glaze  them,  and 
these  temperatures  have  a  killing  influence  on  prac- 
tically everything  except  fire  clay.  With  the  excep- 
tion of  outside  parts,  the  Revelation  Furnace  is  made 
of  fire  clay,  and  it  will  therefore  withstand  the  block 
body  temperatures  much  better  than  any  other  fur- 
nace now  obtainable.  The  furnace  requires  no  forced 
draft,  an  ordinary  chimney  being  all  that  is  required 
in  this  connection.  The  fuel,  kerosene  oil,  is  obtain- 
able in  all  sections  of  the  globe,  therefore  the  cost  of 
running  the  furnace  is  comparatively  low ;  and  last, 
but  by  no  means  least,  the  worker  is  not  at  the  mercy 
of  gas  or  electric  companies. 

The  size  and  form  of  the  muffle  (8  inches  long,  3^ 
inches  wide,  3  inches  high)  admits  any  piece  of  work 
from  a  small  inlay  to  a  full  denture  of  continuous 
gum,  and  the  even  temperature  obtained  can  be  de- 
pended upon  to  make  the  firing  perfect. 
Operating  the  To  start  this  furnace  it  is  only  necessary 
Revelation  to  open  the  cock  and  allow  the  oil  to  flow 
Furnace  ^^^-^^^j  ^^^^  burner  is  partially  filled,  th  en  light 
the  oil  with  a  match.  Wlien  the  furnace  is  started 
from  the  cold,  it  takes  about  forty  minutes  before  the 
temperature  in  the  muffle  is  sufficiently  high  to  fire 
porcelains  of  the  block  body  class. 

When  any  desired  temperature  is  once  obtained, 
it  is  easily  maintained  by  regulating  the  burner  and 
the  flow  of  oil.  To  stop  the  furnace  it  is  only  neces- 
sary to  close  the  cock  which  controls  the  flow  of  oil, 
thus  allowing  the  oil  in  the  burner  to  be  consumed 
in  a  few  minutes. 

Electric  In  communities  where  the  electric  current 
Furnaces  is  obtainable,  the  electric  furnace  has  found 
favor.  This  type  of  furnace  possesses  many  features 
which  recommend  themselves  to  the  operative  dentist 


110 


GILBERT  S    N'OTES    ON    DENTAL    PORCELAIN 


— they  are  compact,  easily  manipulated,  clean,  and 
noiseless,  and  within  certain  limits  of  temperature 
they  are  efficient  and  durable.  Notwithstanding  the 
fact  that  certain  manufacturers  recommend  their 
electric  furnaces  for  the  firing  of  block  bodies,  the 
advice  is  here  given  to  put  little  faith  in  such  recom- 
mendations. It  is  quite  true  that  some  porcelain  com- 
pounds which  come  under  the  definition  of  block  body 

Fig.  86 


The  Pelton  Furnace  isio.  1 


can  be  glazed  in  the  electric  furnace,  but,  as  stated 
elsewhere  in  this  treatise,  the  obtaining  and  main- 
taining of  such  temperatures  should  be  regarded  in 
the  light  of  experiment  rather  than  good  practice. 
Again  let  it  be  said  that  block  bodies  should  not  be 
fired  in  the  present  type  of  electric  furnace.  For 
high-fusing  and  low- fusing  porcelains  any  of  the  well- 
known,  furnaces,  such  as  the  Pelton,  Hammond,  and 
Custer,  can  be  relied  upon  for  efficiency. 


FURNACES 
Fig.  87 


111 


The  Pelton  Ii'uknace  No.  2 


Fio.  as 


Hammond  Electuic  Fuknace  No.  2 


112       gilbert's  notes  on  dental  porcelain 

Fig.  89 


Hammond  Electric  Fuknace  No.  4,    Closed  and  Open 


FURNACES 
Fig.  91 


113 


Custer  Electric  Furnace  No.    1 
Fig.  92 


CusTEK  Electric  Oven  No.  8 
8 


114       gilbert's  notes  on  dental  porcelain 

These  furnaces  differ  in  construction  and  design. 
(Figs.  86  to  92.) 

Each  possesses  special  features  which  appeal  to 
different  individuals ;  therefore  every  prospective 
porcelain  worker  should  study  these  features  and 
select  the  furnace  best  adapted  to  his  needs.  When 
operating  any  electric  furnace,  the  thought  should  be 
borne  constantly  in  mind  that  the  heat  is  derived 
from  the  resistance  offered  by  platinum  wires  to  the 
passage  of  the  electric  current,  therefore  the  muffle 
cannot  be  heated  too  high  without  danger  of  subse- 
quently causing  a  break  in  the  wire. 

Most  of  the  ''burn  outs"  in  electric  furnaces  are 
caused  by  ignoring  the  above  thought  regarding  the 
relation  of  the  heat  to  the  wires.  Practical  experi- 
ence is  the  only  thing  which  will  make  a  man  pro- 
ficient in  the  manipulation  of  the  electric  furnace; 
but  if  the  novice  will  refrain  from  attempting  to  fire 
porcelain  compounds  having  a  glazing  point  too  high 
for  the  furnace,  and  will  make  it  a  rule  to  obtain  no 
higher  temperature  than  is  required  to  glaze  high- 
fusing  porcelain  in  a  reasonable  length  of  time,  he 
will  have  little  difficulty  in  keeping  the  electric  fur- 
nace in  good  working  condition. 

GASOLINE  FURNACES 

In  small  towns  and  country  places  where  the  elec- 
tric current  is  not  available,  gasoline  furnaces  can  be 
depended  upon  to  fire  the  high-fusing  porcelains. 
They  are  preferred  by  some  dentists  in  localities 
where  the  electric  current  is  available,  this  prefer- 
ence being  occasioned  by  the  thought  that  the  gaso- 
line furnace  is  less  liable  to  burn  out  and  its  mainte- 
nance costs  less  than  the  electric  furnace.  Furnaces 
of  this  type  are  shown  in  Figs.  93  and  94. 


FURNACES 
Fig.  93 


115 


Turner  Gasoline  Furnace  No.   140 


Fig.  94 


Turner  Gasoline  Furnace  No.  41 


116 


GILBERT  S    NOTES    OX    DEXTAL    PORCELAIN 


GAS  FURNACES 

Several  types  of  gas  furnaces  have  been  offered 
as  being  entirely  suitable  for  the  firing  of  dental 
porcelains.  Most  of  these  have  been  withdrawn  from 
the  market  through  the  lack  of  commercial  demand. 
Of  those  which   are   now   offered   for   sale,   Ball's 


Fig.  95 


Simple  Furnace  and  the  Jenkins  Miniature  Gas  Fur- 
nace can  be  especially  recommended.  The  Simple 
Furnace  (Fig.  95)  was  designed  by  Dr.  Dall,  of  Glas- 
gow, and  is  neat  in  form  and  design.  It  is  compact, 
comparatively  noiseless,  and  it  can  be  relied  upon  to 
properly  glaze  inlays  and  crowns  made  from  the 
Jenkins  Porcelain  Enamel,  Ash's  Low-  and  High- 
Fusing  Porcelains,  White's  Medium-  and  High- 
Fusing  Porcelains.  The  Miniature  Gas  Furnace 
(Fig.  96),  designed  by  Dr.  Jenkins,  has  been  espe- 
cially constructed  to  properly  fire  the  Jenkins  porce- 
lain, and  for  this  purpose  it  is  considered  superior  to 


FURNACES 


117 


any  other  design.  This  ^Miniature  Furnace,  as  its 
name  implies,  is  smalL  It  is  neat  in  appearance  and 
comparatively  noiseless.  The  muffle  is  provided  with 
an  opening  in  the  bottom  through  which  the  flame  of 
gas  can  be  directed,  thus  heating  the  invested  porce- 
lain from  the  bottom.     The  opening  in  the  front  of 

Fig.  96 


the  muffle  is  large  enough  to  permit  a  full  view  of  the 
glazing  process,  and  it  also  ])ermits  easy  manipula- 
tion of  the  investment.  Owing  to  the  fact  that  the 
eTenkins  porce'ain  yields  its  best  results  when  the 
heat  is  directed  from  l)elow,  and  that  it  flows  by  grav- 


118        gilbert's  notes  on  dental  porcelain 

ity  when  melted,  botli  of  these  openings  are  of  great 
advantage. 

The  Jenkins  Furnace,  which  fills  every  require- 
ment for  firing  the  Jenkins  porcelain,  is  not  adapted 
for  firing  porcelains  the  glazing  point  of  which  is 
considerably  higher. 


CHAPTER   X 


FIRING  PORCELAIN 

The  denture,  bridge,  crown,  or  inlay  which  is  to  be 
fired  must  be  placed  on  a  suitable  conveyance  pre- 
vious to  placing  it  in  the  furnace. 

For  dentures,  a  slide  like  that  shown  in  Fig.  97 
should  be  covered  with  silex  and  the  denture  laid 
upon  it,  building  up  where  necessary  to  support  the 
porcelain  during  the  glazing  process. 

Fig.  97 


Fire- Clay  Slide 
Shown   A  size 


Fig.  OS 


For  bridges  and  crowns,  fire-clay  supports,  pro- 
vided with  slots  and  holes  for  the  reception  of  anchor- 
l^ins,  are  essential.  (Fig.  98.) 

For  inlays,  either  fire-clay  or  platinum  pans  are 
indicated.  All  block  bodies  and  most  of  the  high- 
fusing  porcelains  can  be  placed  in  a  hot  furnace  after 
all  moisture  has  been  driven  out  of  the  porcelain  and 

119 


120       gilbert's  notes  on  dental  porcelain 

the  object  gradually  heated  to  redness.  The  prelimi- 
nary drying  out  and  heating  is  best  accomplished  by 
opening  the  door  of  the  furnace,  placing  the  object 
to  be  fired  far  enough  away  to  prevent  too  rapid 
heating,  then  bringing  it  gradually  up  to  the  opening 
of  the  muflfie,  then  when  thoroughly  heated  placing 
it  in  the  muffle  and  closing  the  door.  In  firing  some 
of  the  high-fusing  porcelains  and  all  of  the  low- 
fusing  it  is  necessary  to  start  with  the  temperature 
in  the  furnace  very  low.  If  this  precaution  is  not 
taken,  and  the  effort  is  made  to  fire  under  the  same 
conditions  mentioned  for  firing  block  bodies  and  some 
high-fusing  porcelains,  there  will  be  difficulty  in  pro- 
ducing desired  shades  and  a  porcelain  free  from 
white  edges.  Experience  only  will  show  the  worker 
how  each  grade  of  porcelain  should  be  fired  in  order 
to  derive  the  best  results.  After  the  furnace  door 
has  been  closed,  one  of  the  most  difficult  problems  of 
porcelain  work  is  presented  to  the  worker,  i.  e.,  How 
shall  I  know  when  the  porcelain  is  properly  glazed"? 
The  solution  of  this  problem  is  by  no  means  as  diffi- 
cult as  some  men  would  have  us  believe,  neither  is  it 
so  easy  that  it  can  be  taught  by  cold  type.  In  the 
Recognition  first  place,  every  worker  who  expects  to 
of  Glaze  fire  porcelain  must  learn  to  recognize  the 
glaze  upon  its  surface  according  to  his  own  indi- 
vidual idea  of  what  that  glaze  should  be.  There  is 
a  wide  difference  of  opinion  relative  to  the  amount 
of  glaze  which  should  appear  in  an  artificial  tooth, 
a  crown,  or  an  inlay.  The  degree  of  glaze  which 
one  individual  would  call  i)erfect  or  desirable  would 
be  recognized  by  another  individual  as  "short  of 
glaze,"  or  by  another  as  "overglaze."  so  each  indi- 
vidual must  fix  in  his  own  mind  his  idea  of  a  proper 
glaze. 


FIRING     PORCELAIlSr  121 

To  recognize  the  glaze  upon  a  piece  of  cold  porce- 
lain held  in  the  hand,  where  it  can  be  turned  about  at 
will  and  viewed  in  different  positions,  is  one  thing, 
and  to  recognize  this  same  glaze  when  the  piece  is  hot 
is  quite  another  thing,  but  this  recognition  is  easily 
acquired  with  practice. 

In  the  firing  of  some  low-fusing  porcelains,  like 
the  Jenkins  porcelain  enamel  and  Ash's  low- fusing, 
the  muffle  can  remain  open  and  the  process  of  glazing 
can  be  watched  throughout.  Block  bodies  and  high- 
fusing  porcelains  require  considerably  higher  tem- 
peratures to  glaze  them,  and  the  glow  produced  by 
the  heat  upon  the  porcelain  and  its  surroundings  will 
not  permit  of  constant  watching,  therefore  some 
means  must  be  devised  for  determining  when  the 
Methods  for  glazing  of  the  porcelain  takes  place.  Vari- 
Determining  ous  methods  and  devices  have  been  sug- 
Glaze  gested  for  determiniiig  the  time  when  a 

porcelain  product  should  be  removed  from  the  fur- 
nace; some  of  these  will  be  detailed  as  follows.  The 
method  generally  pursued  depends  upon  the  worker's 
familiarity  with  the  appearance  of  the  ''fire"  and 
the  time  (by  watch)  which  a  given  porcelain  will 
require.  For  example :  A  Revelation  Oil  Furnace  is 
being  used  to  fire  an  artificial  denture  made  of  a 
block  body.  The  temperature  of  the  muffle  is  raised 
to  a  point  which  the  worker  judges  with  his  eye  to 
be  right  for  the  glazing  of  the  particular  porcelain 
in  use.  This  judgment  of  temperature  by  the  eye 
can  be  relied  upon  as  being  approximately  correct 
providing  the  worker  has  had  long  experience.  When 
the  proper  working  temperature  is  thus  obtained,  the 
denture,  which  should  be  on  a  fire-clay  slab,  is  placed 
in  front  of  the  muffle  and  allowed  to  remain  until  all 
moisture  has  been  driven  out  and  the  porcelain  be- 


122       gilbert's  notes  ojn   dental  porcelain 

gins  to  warm  up.  When  the  preliminary  heating  has 
taken  place,  the  denture  should  be  pushed  back  in  the 
Time  muffle,  the  door  closed,  and  the  case  timed. 

and  Eye  Timing  the  firing  is  necessarily  a  matter 
of  experience:  it  is  subject  to  the  judgment  of  the 
worker.  He  knows  the  "fire,"  knows  the  porcelain, 
and  after  closing  the  muffle  door  he  relies  first  upon 
his  watch  and  finally  upon  his  eye. 

If  experience  has  taught  him  that  three  minutes 
is  required  to  glaze  the  porcelain,  he  allows  three  min- 
utes to  elapse,  opens  the  door  of  the  muffle,  withdraws 
the  case,  looks  at  it,  and  if  glazed  he  removes  it  to 
the  annealing  oven.  If  not  properly  glazed,  the  case 
is  pushed  back  in  the  muffle  and  given  a  longer  fire. 
In  cold  type  the  above  method  of  firing  porcelain 
appears  very  crude,  and  it  is  at  the  best  uncertain, 
although  it  is  thoroughly  practical,  and  when  pur- 
sued by  experienced  workers  the  results  are  satis- 
factory. When  the  supply  of  electric  current  is  uni- 
form, an  electric  furnace  can  be  employed  to  glaze 
porcelain  by  the  timing  method  with  some  degree  of 
certainty.  The  worker  quickly  learns  by  experiment 
that  when  the  lever  of  the  rheostat  is  upon  a  given 
contact,  it  requires  a  definite  length  of  time  to  prop- 
erly glaze  a  given  porcelain. 

Porcelain  Another  method  of  glazing  the  block  bodies 
Cones  and  high-fusing  porcelains  depends  upon 

"test  pieces"  placed  alongside  of  the  object  which  is 
being  fired.  A  cone  of  porcelain  (Fig.  99),  for  exam- 
ple, is  made  of  the  same  material  as  the  denture  or 
crown.  This  cone  is  dried  out  and  heated  just  the 
same  as  the  pieee  which  is  being  made;  both  are  then 
placed  in  the  muffle  and  the  door  closed.  As  the  firing 
progresses,  the  door  of  the  furnace  can  be  opened  and 
the  point  of  the  cone  observed  by  the  eye.    Wlien  the 


FIRING     PORCELAIN  123 

point  assumes  an  outline  like  that  shown  in  Fig.  100, 
the  glazing  is  complete;  but  if  there  be  a  doul)t  in 
the  mind  of  the  worker,  he  can  remove  the  cone  from 


Fig.  09  Fig.  100 


the  furnace  and  examine  it  in  daylight.  The  glaze 
on  the  cone  will  be  practically  the  same  as  that  on 
the  object  being  fired. 

Gold  and  Another  method,  and  one  which  can  be  fol- 
Time  lowed  with  more  or  less  success,  depends 

upon  the  melting  of  pure  gold  as  a  guide.  A  small 
quantity  of  foil  gold  is  pinched  with  the  fingers  to 
form  a  cone  or  pyramid.  This  is  placed  in  the  muffle 
on  a  piece  of  fire  clay  alongside  of  the  work  and 
watched  until  it  melts  or  assumes  a  pellet  form. 
After  the  gold  melts,  a  given  length  of  time  by  the 
watch  is  allowed  to  elapse  before  the  porcelain  work 
is  removed  from  the  furnace. 

The  particular  length  of  time  required  to  glaze  a 
given  porcelain  after  the  gold  melts  must,  of  course, 
be  learned  by  experiment  before  this  method  of  deter- 
mining the  glaze  can  be  depended  upon.  The  time 
required  will  vary  in  the  different  furnaces.  A 
porcelain  which  requires  one  minute  after  gold  in  one 
furnace  may  require  only  thirty  seconds  in  another 
and  perhaps  a  minute  and  thirty  seconds  in  another 
furnace ;  so,  as  before  stated,  if  this  method  of  firing 
is  to  be  pursued,  the  worker  must  do  some  experi- 
menting with  each  grade  of  porcelain  and  each  fur- 
nace before  making  a  practical  application.    Another 


124       gilbert's  kotes  on  dental  porcelain 

practical  method  of  determining  the  time  when  a 
piece  of  porcelain  work  is  properly  glazed  is  by  the 
use  of  the  little  pyrometer  (Fig.  101),  devised  by  Dr. 
D.  0.  M.  Le  Cron,  St.  Louis. 

Fig.  101 


Pyrometer  This  pyrometer  consists  of  a  fireproof  re- 
Metal  ceptacle  and  a  metal  pellet  or  pellets.  Dif- 
ferent pellets  are  made  of  alloj^s  having  different 
melting  jooints  corresponding  to  the  glazing  points 
of  different  porcelain  compounds. 

Suppose  a  worker  is  desirous  of  firing  a  crown 
made  of  The  S.  S.  White  Dental  Mfg.  Co.'s  High- 
Fusing  Porcelain :  He  selects  the  pellet  the  melting- 
point  of  which  corresponds  with  the  glazing  point  of 

Fig.  102 


the  porcelain  mentioned,  places  it  on  the  top  of  the 
fireproof  cup,  and  then  places  the  crown  and  pyrom- 
eter side  by  side  in  the  muffle  of  the  furnace.  As  the 
glazing  point  of  the  porcelain  is  approached  the  metal 
pellet  softens  and  elongates  until  it  drops  into  the 
bottom  of  the  cup.  (Fig.  102.)  When  this  occurs,  the 
porcelain  crown  is  glazed,  and  the  heat  can  be  dimin- 
ished or  the  crown  removed  from  the  furnace  accord- 
ing to  the  method  of  cooling  pursued  by  the  worker. 


FIRING     PORCELAIN  125 

About  the  only  objection  that  can  be  raised 
against  this  way  of  firing  is  that  of  having  to  look 
into  the  glow  of  the  heat,  but  this  objection  is  theo- 
retical rather  than  practical.  The  simplicity  and 
cost  of  the  device  and  the  many  advantages  derived 
from  its  use  more  than  offset  any  minor  objections 
like  the  one  mentioned.  When  the  pellet  melts,  cut  off 
the  heat  or  remove  the  piece  from  the  muffle.  That 
is  the  method  of  solving  the  much-mooted  question  of 
firing  dental  porcelains. 

Various    kinds    of    pyrometers    have    for 
PyroniotGrs 

many  years  been  employed  to  determine 

the  temperature  in  places  not  visible  to  the  eye. 

The  simplest  form  of  these  is  the  Segar  pyrom- 
eter cones,  which  are  made  after  various  formulas 
capable  of  recording  temperatures  ranging  from  that 
necessary  to  fuse  glass  up  to  that  required  to  melt 
platinum  and  "to  determine  the  fireproofness  of  clay 
and  other  like  material." 

Practical  dental  application  of  the  principle 
involved  by  the  Segar  cone  has  been  previously 
described.  Pja-ometer  metal  has  for  a  long  time 
been  used  in  the  potter's  industry.  These  metals 
or  alloys,  like  the  Segar  cones,  are  made  after  dif- 
ferent formulas  capable  of  recording  wide  ranges 
of  temperatures.  A  little  strip  of  the  pyrometer 
metal  is  placed  alongside  of  the  porcelains  to  be  fired, 
and  when  the  metal  assumes  the  form  of  a  pellet  the 
proper  temperature  has  been  obtained.  Dr.  Le  Cron's 
pyrometer,  jDreviously  described,  is  a  practical  dental 
application  of  the  pyrometer  metal,  or,  as  it  is  some- 
times called,  Princeps  alloy.  Thermo-electric  indi- 
cating pyrometers  of  recognized  merit  are  now  ob- 
tainable, and  these  can  be  relied  upon  to  give  prac- 
tical results  in  the  firing  of  all  dental  porcelains. 


CHAPTER    XL 


SUGGESTIONS  FOR  USING  THERMO-ELECTRIC 
PYROMETERS 

As  stated  in  the  closing  words  of  the  last  chapter, 
l)yrometers  of  recognized  merit  are  now  o1)tainable, 
and  they  can  be  depended  upon  to  give  practical  re- 
sults in  the  firing  of  dental  porcelains.  This  state- 
ment is  true,  but  it  should  not  be  accepted  to  mean 
that  these  pyrometers  will  indicate  the  glazing  point 
of  a  given  porcelain  in  the  same  sense  as  a  clock  indi- 
cates the  flight  of  time.  That  is,  something  more 
than  a  sim]3le  watching  of  the  pyrometer  indicator  is 
necessary  to  determine  the  proper  glaze  on  an  inlay, 
crown,  denture,  or  bridge. 

The  thermo-electric  pyrometer  is  a  scientific  in- 
strument devised  for  the  purpose  of  determining 
definite  methods  of  producing  desired  results,  there- 
fore, it  must  be  used  scientifically  if  it  is  to  be  used 
effectively.  Before  attempting  to  use  the  thermo- 
electric pja^ometer  it  must  be  thoroughly  understood 
by  the  operator  that  the  proper  glazing  of  all  dental 
porcelains  is  dependent  upon  both  time  and  temper- 
ature. Remember  that  it  cannot  arbitrarily  and 
truthfully  be  stated  that  a  given  grade  of  porcelain 
fuses  or  takes  the  glaze  at  a  given  temperature,  but 
it  may  be  truthfully  stated  that  a  given  porcelain 
can  be  fused  or  glazed  if  subjected  to  a  given  tem- 
perature for  a  given  length  of  time.    The  dentist  who 

12G 


SUGGESTIONS    FOR     USING    PYROMETERS 


127 


purchases  and  uses  a  pyrometer  with  a  full  under- 
standing of  the  above  facts  will  conserve  time  and 
energy  and  will  feel  amply  repaid  for  the  expendi- 
ture of  money  necessary  to  place  a  pj^rometer  at  his 
service. 


Fig.   103. 


Thermo-Electric  Pyrometers  as  now  manufac- 
tured for  use  by  the  dentist  are  attached  to  the 
furnace  in  two  ways. 

In  one  form  the  thermo-couple  is  attached  per- 
manently to  the  rear  of  the  muffle,  and  in  the  other 
it  is  attached  permanently  to  the  door  of  the  muffle, 


128      gilbert's   notes    on    dental   porcelain 

and  is  therefore  removed  from  the  heat  area  every 
time  the  muffle  door  is  open,  or  removed.  Both 
forms  of  attachment  have  their  advocates  among 
porcelain  workers.      It   is,   therefore,   advisable   to 

Fig.   104. 


study  the  conditions  under  which  the  furnace  and 
pyrometer  are  to  be  used,  and  then  be  governed  in 
the  selection  of  an  outfit  accordingly^ 

Figure  104  shows  the  attachment  of  the  pj^rometer 
to  the  rear  of  the  muffle. 


SUGGESTIONS     FOR     USING    PYROMETERS 


129 


Figures  105  and  106  show  the  attachment  of 
Pyrometer  to  the  front  of  the  muflfle  through  the 
door. 


Fig.   105. 


Fig.    106. 


130      Gilbert's   notes    on    dental   porcelain 

Directions  If  all  pyrometers  and  all  electric  furnaces 
Impractical  were  manufactured  as  exact  duplicates 
and  the  electric  current  was  always  and  at  all  places 
uniform,  and  if  all  individuals  had  the  samu  opinion 
on  the  subject  of  glaze,  then  it  would  be  possible  to 
give  definite  directions  for  using  pyrometer  and  fur- 
nace, but  such  is  not  the  case.  Pyrometers  differ, 
electric  furnaces  are  by  no  means  uniform,  the  elec- 
tric current  is  subject  to  constant  changes  and  the 
opinions  of  dentists  differ,  therefore,  suggestions 
rather  than  directions  will  be  here  given  for  the  use 
of  pyrometer  and  furnace.  ^By  offering  suggestions 
rather  than  directions  the  pyrometer  is  rendered  ap- 
plicable to  the  use  of  all,  notwithstanding  the  lack  of 
uniformity  in  the  manufactured  articles  and  the 
varying  opinions  of  different  individuals. 
Testing  the  Each  outfit  (pyrometer  and  furnace  muf- 
Muffle  fie)  should  be  tested  by  the  dentist  for  the 

purpose  of  ascertaining  the  temperature  which  can 
be  obtained  in  his  particular  muffle  with  the  control 
lever  of  the  rheostat  on  the  different  contacts.  For 
example :  Place  the  control  lever  on  the  first  contact 
of  the  rheostat  and  allow  it  to  remain  there  until  the 
indicator  on  the  pyrometer  remains  practically  sta- 
tionary. The  figure  in  degrees,  Fahrenheit  or  Centi- 
grade, thus  recorded,  shows  the  temperature  which 
can  be  obtained  by  operating  with  the  lever  on  the 
first  contact.  Continue  the  test  by  recording  the  tem- 
perature obtainable  on  the  second  contact,  the  third, 
and  so  on  until  2500°  F.  has  been  recorded.  Not  all 
furnaces  will  produce  such  a  temperature,  but  with 
those  that  do  it  is  advisable  to  keep  the  temperature 
at  or  lower  than  this  figure.  This  caution  is  given 
because  practical  experience  has  shown  that  it  is  in- 
advisable to  run  any  of  the  present  type  of  electric 


SUGGESTIONS    FOR     USING    PYROMETERS  131 

furnaces  much  beyond  2500°  F.  After  an  experi- 
ment of  this  kind  the  capability  of  the  muffle  becomes 
a  known  quantity,  and  a  further  test,  that  of  glazing 
the  porcelain,  should  be  made. 

Testing  the  If  the  porcelain  under  test  belongs  to  the 
Porcelain  high-fusing  class  the  control  lever  of  the 
rheostat  should  be  placed  on  the  lowest  contact  which 
will  produce  a  temperature  of  at  least  2100°  F. 
When  this  temperature  has  been  obtained,  open  the 
muffle  door,  throw  the  control  lever  back  to  the  first 
contact  and  place  the  porcelain  under  test  in  front  of 
the  muffle  to  dry  out.  When  the  temperature  drops 
to  say  1900°  F.  or  lower,  place  the  porcelain  in  tha 
muffle  and,  if  possible,  directly  under  the  thermo- 
couple. If  the  piece  to  be  fused  is  too  large  to  go 
under  the  thermo-coui^le,  place  it  as  near  the  couple 
as  is  practicable.  Throw  the  control  lever  on  the 
fusing  contact  (the  lowest  contact  which  gives  2100° 
F.),  and  when  the  jDyrometer  registers  1900°  F. 
close  the  door  of  the  muffle  and  watch  the  indicator 
on  the  pyrometer.  When  2100°  F.  is  recorded, 
throw  the  control  lever  back  on  the  first  contact, 
open  the  muffle  door  and  remove  the  porcelain. 
If  the  contact  which  affords  2100°  F.  does  not  glaze 
the  porcelain,  try  the  next  contact  which  will  give  a 
higher  temperature,  and  so  on  until  the  proper  con- 
tact and  temperature  is  ascertained.  When  the  right 
contact  and  right  temperature  have  been  thus  deter- 
mined for  correctly  glazing  a  given  porcelain,  the 
same  procedure  will  indefinitely  duplicate  results 
unless  the  voltage  of  the  electric  current  is  contin- 
ually changing.  To  make  this  method  of  using  the 
pyrometer  plainer,  take  as  an  ilhistration  the  glaz 
ing  of  two  popular  porcelains,  viz.,  The  S.  S.  White 
Dental     Manufacturing     ('omi)any's     High-Fusing 


132      gilbert's   notes    on    dental   porcelain 

Porcelain  and  C.  Ash  &  Sons  High-Fusing  Mineral 
Body,  using  a  Hammond  Pyrometer  and  Hammond 
Furnace  when  making  the  experiment. 

The    fusing   temperature    of    The    S.    S. 

White  Dental  Manufacturing  Company's 
High-Fusing  Porcelain  is  about  2360°  F.  The  degree 
of  glaze  which  suits  some  individuals  may  require 
2340°  or  2360°,  but  whatever  temperature  is  found  to 
give  the  desired  results  that  is  the  one  to  work  to. 
2300°  F.  is  used  in  this  suggestion  merely  as  an  illus- 
tration; therefore,  test  the  muffle  to  determine  the 
lowest  contact  which  will  produce  2300°  F.  The 
contact  necessary  to  produce  this  temperature  may 
be  the  fifth,  the  fourth  or  even  the  third,  depending 
on  the  current  voltage  and  the  muffle  wiring,  but 
every  time  the  lever  is  placed  on  that  contact  there- 
after a  temperature  of  about  2300°  F.  will  be  indi- 
cated by  the  pyrometer.  Having  found  the  con- 
tact that  gives  the  proper  temperature,  it  establishes 
a  fixed  point  to  which  to  work.  The  details  of 
procedure  would  be  as  follows :  Make  several  test- 
pieces  of  the  porcelain   (see  Fig.   107),   and  place 

Fig.    107. 


them  on  top  of  the  furnace  to  dry  out.  Place 
the  control  lever  on  the  lowest  contact  which  recoi-ds 
2300°  F.  or  thereabouts.  When  dry,  place  one  of  the 
test  ijieces  on  a  fire-clay  slide,  throw  back  the  lever  to 
the  first  contact,  open  the  door  of  the  muffle  and  place 
the  test  piece  in  front  of  the  muffle.    Pay  no  attention 


SUGGESTIONS    FOR    USING    PYROMETERS  133 

to  the  piece,  but  observe  when  the  pyrometer  indi- 
cates 1900°  F.  or  slightly  below.  (Some  muffles  are  so 
well  wound  that  a  high  temperature  is  developed 
with  the  lever  on  the  first  contact,  making  it  impos- 
sible to  get  down  to  1900°  F.  on  this  contact.  If  this 
is  the  case  with  the  muffle  under  test,  break  the  cur- 
rent by  opening  the  knife-switch.)  Place  the  porce- 
lain testpiece  in  the  muffle  and  as  near  the  thermo- 
couple as  is  practicable.  Throw  the  lever  of  the 
rheostat  on  the  contact  which  records  2300°  F.  Close 
the  door,  and  when  the  indicator  registers  2300°  F,, 
open  the  muffle  and  remove  the  porcelain.  As  before 
stated,  while  2300°  F.  is  mentioned  as  the  degree 
which  indicates  the  proper  glaze,  it  is  not  to  be 
considered  arbitrary,  for  the  reason  that  several 
degrees  more  or  less  may  give  the  degree  of  glaze 
which  is  preferred  by  different  individuals. 
Another  C.  Ash  &  Sons  High-Fusing  Mineral  Body 

Example  glazes  in  a  temperature  of  approximately 
1900°  F.,  therefore,  the  method  of  glazing  this  porce- 
lain can  be  outlined  as  follows :  Place  the  control 
lever  of  the  rheostat  on  the  lowest  contact  which  will 
record  1900°  F.  After  heating  the  muffle  to  this 
temperature,  drop  the  temperature  to  say  1500°  F.  or 
thereabouts  (this  can  be  accomplished  by  either  using 
a  lower  contact  or  by  breaking  the  current.)  Place 
the  porcelain  testpiece  in  the  muffle  and  under,  or  as 
near  as  possible  to,  the  thermo-couple.  Throw  the 
lever  of  the  rheostat  on  the  contact  which  records 
1900°  F.  When  1500°  F.  is  recorded,  close  the  door 
of  the  muffle,  and  when  the  pyrometer  registers 
1900°  F.,  open  the  door  and  remove  the  porcelain. 

It  must  not  be  understood  that  the  method  just 
suggested  is  the  only  one  which  can  be  depended 
upon  to  give  satisfactory  I'esults  in  the  glazing  of 


134       gilbert's  notes  on  dental  porcelain. 

porcelain,  for  such  is  not  the  case.  There  are  sev- 
eral other  methods,  among  which  can  be  mentioned 
Another  the  following :     The  method  of  ascertain- 

Method  ing  by  experiment  just  what  temperature 

and  what  time  is  required  to  glaze  a  given  porcelain, 
and  then  pursue  the  following  detail :  Keep  the  tem- 
perature in  the  muffle  at  the  desired  figure  by  shift- 
ing the  lever  of  the  rheostat ;  place  the  porcelain  to 
be  glazed  in  the  muffle — this  will  cause  the  tempera- 
ture to  drop  many  degrees,  but  it  is  soon  brought 
back  to  the  desired  degree — and  allow  a  given 
amount  of  time  to  elapse,  then  open  the  door  of  the 
muffle  and  remove  the  work. 

For  example :  To  glaze  a  crown  made  of  The  S.  S. 
White  Dental  Manufacturing  Company's  High-Fus- 
ing Porcelain,  raise  the  temperature  in  the  muffle  to 
at  least  2300°  F.,  place  the  crown  (which  should  be 
free  from  all  moisture)  in  the  muffle,  close  the  door, 
watch  the  pyrometer,  and  when  the  indicator  regis- 
ters 2300°  F.,  take  an  account  of  the  time,  keeping 
the  pyrometer  at  2300°  F.,  and  allow  one-  and  one- 
half  minutes  to  pass,  after  which  immediately  re- 
move the  crown.  Different  bulks  of  porcelain  will  re- 
quire different  lengths  of  time,  but  this  variation  in 
time  is  readily  ascertained  by  experiment. 
First  Method  Of  the  two  methods  above  suggested  for 
Preferable  the  use  of  the  pyrometer  and  furnace,  the 
first  is  preferable — first,  because  it  caters  to  the  pe- 
culiar characteristics  of  porcelain,  and  second,  it  is 
better  adapted  to  the  practical  working  methods  of 
the  dentist.  Generally  speaking,  all  dental  porcelains 
should  be  gradually  heated  from  the  room-tempera- 
ture to  the  temperature  required  to  produce  the 
glaze ;  in  fact,  some  must  be  treated  in  this  way  in 
order  to  insiii-e  form  and  color.     The  method  first 


SUGGESTIONS    FOR    USING    PYROMETERS  135 

suggested  is  based  upon  this  observation,  and  it  will 
be  found  that  if  porcelain  is  treated  in  this  way,  bet- 
ter results  will  be  secured  than  in  the  pursuance  of  a 
method  which  subjects  the  cold  porcelain  immedi- 
ately to  its  glazing  temperature. 

Aside  from  the  fact  that  dental  porcelains  should 
be  gradually  heated  to  their  glazing  temperature,  the 
method  which  provides  for  such  treatment  facilitates 
the  work  of  the  dentist  by  eliminating  eye-strain  and 
nervous  tension,  and  it  insures  diying  out  without 
the  loss  of  any  time. 

Use  the  thermo-electric  pyrometer  simp]y 
as  a  device  for  duplicating  results  in  the 
firing  of  dental  porcelains. 

The  method  of  using  is  a  matter  to  be  decided  upon 
by  the  individual  operator.  As  stated  in  the  fore- 
going pages,  absolute  directions  for  the  use  of  this 
instrument  are  of  little  practical  value;  and,  fur- 
thermore, let  it  be  thoroughly  understood,  that  the 
methods  outlined  are  only  suggestions. 
Criticism  of  Any  device  or  instrument  which  may  be 
Pyrometers  used  to  determine  the  glaze  upon  porcelain 
will  be  subject  to  adverse  criticism,  unless  it  be  used 
with  intelligence.  It  will  not  do  for  any  one  indi- 
vidual to  arbitrarily  say  that  the  melting  point  of  a 
given  alloy  will  produce  a  glaze  upon  a  given  porce- 
lain which  will  be  satisfactory  to  every  worker; 
neither  will  it  do  to  say  that  a  definite  number  of 
degrees  of  temperature  will  produce  a  glaze  accept- 
able to  every  one.  Individual  workers  will  have  their 
own  peculiar  ideas  relative  to  the  amount  of  glaze 
which  a  porcelain  should  receive,  and  they  will  have 
to  establish  temperatures  by  the  aid  of  devices  or 
instruments  which  will  meet  their  own  requirements. 
In  the  case  of  the  Le  (h'on    pyrometer,  the  manufac- 


136       gilbert's  notes  on  dental  porcelain. 

turer  might  supply  an  alloy  the  melting  point  of 
which  would  agree  with  his  (the  manufacturer's) 
idea  of  a  proper  glazing  point,  but  a  worker  desiring 
less  glaze  or  more  glaze  upon  the  same  porcelain 
would  not  be  satisfied  to  accept  the  alloy  of  the  manu- 
facturer as  his  (the  worker's)  guide.  This  same 
statement  is  true  regarding  the  use  of  a  pyrometer 
which  records  definite  degrees  of  temperature.  Two 
thousand  degrees  Fahrenheit  may  be  the  figure  arbi- 
trarily stated  by  anyone  to  be  the  correct  glazing 
temperature  of  a  given  porcelain,  but  this  statement 
does  not  necessarily  have  to  be  accepted  by  every 
worker  as  being  correct.  Because  an  instrument 
viewed  in  connection  with  printed  statements  may  be 
subject  to  the  criticism  just  cited,  condemnation  of 
the  instrument  should  not  follow.  The  device  or  in- 
strument may  be  perfectly  satisfactory,  but  the  judg- 
ment of  the  worker  may  be  defective.  In  the  case  of 
the  LeCron  device  the  worker  can  lower  or  raise  the 
melting  point  of  the  alloy  to  meet  with  his  own  ideas 
of  glaze,  or  in  the  case  of  a  temperature-recording 
instrument  he  will  experiment  and  determine  the 
temperature  which  will  produce  the  correct  glaze  as 
he  views  it.  The  consideration  of  time  in  connection 
with  temperature  is  highly  important  when  operating 
a  temperature-recording  pyrometer.  Experiments 
should  be  conducted  by  each  worker  with  the  object 
in  view  of  establishing  the  temperature  and  time 
required  to  derive  the  best  results  from  the  porce- 
lain compound  in  use.  Is  it  best  to  subject  this 
porcelain  to  a  high  temperature  for  a  short  time, 
or  is  it  best  to  subject  it  to  a  low  temperature  for 
a  long  time?  This  question  should  be  asked,  and 
answered  by  the  worker  as  he  attempts  to  use  the 
various  compounds. 


COLUMBIA  UNIVERSITY   LIBRARIES 

This  book  is  due  on  the  date  indicated  below,  or  at  the 
expiration  of  a  definite  period  after  the  date  of  borrowing,  as 
provided  by  the  library  rules  or  by  special  arrangement  with 
the  Librarian  in  charge. 

DATE  BORROWED 

DATE  DUE 

DATE  BORROWED 

DATE  DUE 

. 

C28  (449)  M50 

RK655  ^                  G37 

1906 

Gilbert 

Notes  on  dental  pocelain 

1 

.,  . . 

my^'^ 

r             6-3V 

i   :; 

f   ■ 
;3,    ., 

.1, 
,1 

i 

ii 

; 

.1 

X 

■  I 

:; 

t 

'1 
\ 

